Stalls out when hot - won't restart. Stutter/stumble on accelleration

Merry Christmas!

So, I got the jeep running yesterday and was quite pleased. Drove it around for about 5-10 minutes and everything seemed to be running well.
(http://www.naxja.org/forum/showthread.php?t=1051074)

Later on, took it for a longer drive, on the freeway up to 60-65 and everything seemed fine at first. After about 10-20 minutes it started exhibiting a slight stutter (or lug) and would sputter if you stepped hard on the gas.

Got off the freeway, came to a stop. It was pointed uphill at that point in case that matters -- and when I tried to go again after stopping (stopped for about 10 seconds at red light)as soon as the load was on the engine it lugged hard and stalled out. It would not restart -- right back to the crank no start I was seeing before (see link above).

I was didn't have time to look into anything at all -- so I just got it safely out of the way, and got it towed back to my house a bit later. I haven't had much time to look at anything, but I'm really curious if anyone has any insight on this -- the last time it failed out like this was after a drive of about the same length -- so whatever it is, seems to act up only after the engine (or compartment) is heated up.

Just went and started it up again -- started up (little hard on the start, had to crank 4-5 seconds before catching) and idles okay. When you give it gas there is a definite stutter before it catches -- and if you push hard on the accelerator, it stutters severly; thought it was going to die but it stayed up and settled down when I let off the accel pedal.

Any ideas? I know it is Christmas, and I won't have a chance to do a thing to it until tomorrow (definitely got "the look" when going out just to start it and coming back in...) but I'm looking for ideas on what to check out.

I know I'll have to run it around to get the dies while running and won't restart situation back to troubleshoot that -- but I'm hoping the rough running/stutter on accel is related and I can get that resolved before having to deal with the other.

Thanks in advance, and happy holidays to all!

Clogged exhaust system, broken catalyst inside the Cat. Is there a rattle near the CAT at times? Muffler shop will check it for free in most places.

Fuel flow / pressure / delivery volume problem? Check fuel pressure during acceleration with a gauge. Fuel pressure regulator (FPR) may be bad. Check the vac line to the FPR.

Recheck the MAP sensor, and vacuum lines to the MAP!

O2 sensor is on the fritz. Test it with an analog volt meter. Also disconnect it, and see if the stutter stops completely.

Cracked dizzy cap, bad bearings in the dizzy.....various assorted morphidite electron grimlins in the ignition system.

CPS problem. Bad primary H-Voltage plug wire from coil to dizzy.

Ecomike said:

Clogged exhaust system, broken catalyst inside the Cat. Is there a rattle near the CAT at times? Muffler shop will check it for free in most places.

Fuel flow / pressure / delivery volume problem? Check fuel pressure during acceleration with a gauge. Fuel pressure regulator (FPR) may be bad. Check the vac line to the FPR.

Recheck the MAP sensor, and vacuum lines to the MAP!

O2 sensor is on the fritz. Test it with an analog volt meter. Also disconnect it, and see if the stutter stops completely.

Cracked dizzy cap, bad bearings in the dizzy.....various assorted morphidite electron grimlins in the ignition system.

CPS problem. Bad primary H-Voltage plug wire from coil to dizzy.

Click to expand...

Thanks Eco -- I have yet to notice any noise at all from the CAT or elsewhere in the exhaust. There is a slightly dented section where the exhaust pipe was pinched (I do me extremely slight) upstream of the cat; but it has never been an issue. Replacing the exhaust is 'on the list'. Hopefully that's not an issue, but if everything else checks out I'll return to that as a possible fix.

I just spent the last hour or so filling my head with the Sensor/Renix testing information from the link I keep seeing JP post; http://www.lunghd.com/Tech_Articles/Engine/Basic_Sensors_Diagnostics.htm -- I'll check everything on that list as well as the fuel line tests from that same site tomorrow (assuming such activities are deemed okay on the day after Christmas...)

Good luck.

And don't worry about "the look", after 10 or 20 years you build up enough scar tissue on the back of your neck it won't burn quite as much.

Renix sensor readings forthcoming -- once I get it running again.

Took the fuel pressure test; 30-31 PSI while running at idle - disconnecting the vacuum from the regulator shoots it up to 38-39; so that seems right on spec.

Decided to see what it did while opening the throttle; with slow, gradual opening it stayed fairly steady at 31. if I opened the throttle more quickly -- the engine stuttered as expected, and the PSI kicked up over 40. I released the throttle and the engine and fuel pressure quickly returned to normal. I repeated it, but held the throttle open this time -- not all the way to WOT -- and it stutters and sputtered and died.

It has now returned to the state of cranking the engine with no start/catch (sputtered once or twice but that was it); exactly like it was before. Does this sound like a fuel delivery problem, or is that kind of fuel pressure fluctuation normal/okay?

Back out to take sensor readings....

Took readings on sensors.

CTS: Right after the engine died off it as at 4.72 k ohms (my thermometer said 64F Seems okay.

MAT: About 25 minutes later, 9.06k ohms

MAP (engine not running): Supply 5V, output 4.7 V

CPS: Resistance = 255 ohms (I haven't been able to get the lady to come crank it over to see the AC V output from the sensor yet...I just get looks.)

TPS: Supply 5V
closed: 0.65 V (seems low?)
WOT: 4.3V
Increase from closed to WOT seems pretty smooth, but I only have a digital MM, so that's from what I can see there.

I wasn't able to get a good reading on the O2 sensor -- not sure if that is my retarded probing skills or not as it is not in an easy spot to hold two leads in place and read a meter. /sigh.

I also noticed that my "ballast resistor" (didn't know what that thing was previously) was no longer on the bulkhead by the egr; but laying down below it. Taped together. That an issue; or is it fine as is?

Fuel pressure (without running it) seems to come right up to 31 when the pump primes and slowly falls off again. I had let it sit for a full 30 minutes and it dropped down to 16 PSI at that point. Still uncertain about the spike in pressure when depressing the throttle and how that relates to the sputter and stall. Is that flooding the engine? Would that imply my injectors are shot/shoddy?
I know, I'm going to be told to get a noid light -- and I'm not sure what that is, but I'll just hope it's not a joke to make the parts guy look at me funny. Only noid I'm familiar with was on dominos commercials in the 80's...

Thanks again for looking this over and providing insight/guidance/help. Let me know if there's something I can measure/check that would help you help me!

Mace

"CTS: Right after the engine died off it as at 4.72 k ohms (my thermometer said 64F Seems okay."

If the engine coolant was at 60 to 55 F when you tested the CTS that is OK, if it was hot running, like 100 F or higher, it is a bad CTS.

"MAT: About 25 minutes later, 9.06k ohms"

That would make the manifold and the air in the manifold only about 35 F? So it may be bad also.

It is not so much the ambient air temp as the coolant temp in the engine block when testing the CTS resistance and the manifold metal temp (which can be hot after running the engine as it sits over the exhaust manifold) that you need to know and measure. Static air in a manifold, engine off, will quickly reach the manifold air temp. Keep in mind you need to test the CTS and MAT at 2 extreme temps, hot, and cold to completely verify they are good. A single test at a single temp only confirms it is not shorted, not open, and that it reads that one temp correctly. If reads 5000 ohms at 20 F and 200F it is bad!


"MAP (engine not running): Supply 5V, output 4.7 V"

That needs to be tested with a vacuum on it next. A manual hand vacuum pump would help there, unless you have a running engine vacuum line to test it with.


"CPS: Resistance = 255 ohms (I haven't been able to get the lady to come crank it over to see the AC V output from the sensor yet...I just get looks.)"

You need to learn how to return that look, or an even scarier one!!!! or try this :kissyou:

"TPS: Supply 5V
closed: 0.65 V (seems low?)
WOT: 4.3V
Increase from closed to WOT seems pretty smooth, but I only have a digital MM, so that's from what I can see there."

.65 at idle is way too low. Needs to be .82 IIRC.

"I wasn't able to get a good reading on the O2 sensor -- not sure if that is my retarded probing skills or not as it is not in an easy spot to hold two leads in place and read a meter. /sigh."

You really need an analog meter for live O2 sensor data. But if it sets at a number, like .5, or 4.5 V and does not budge there is a problem that will run the engine lean or rich. Best way to test for an O2 sensor issue, is just disconnect it. The ECU will then ignore it, and use a rich feed data table for A/F mixture. Bad O2 sensor should not cause a no start, that I know of, but can cause the dying once it is running a little bit.

"I also noticed that my "ballast resistor" (didn't know what that thing was previously) was no longer on the bulkhead by the egr; but laying down below it. Taped together. That an issue; or is it fine as is?"

Depends on what tapped together means? The ballast is bypassed while starting, used to slow the pump while engine is running. It basically gives the fuel pump full battery power while the engine is cranking as the battery drops to about 10 V while cranking. Then with engine running, alternator running the battery is up to 14 volts, so the B.Resistor drops the voltage to the fuel pump to about 12 V to extend the FP life.

"Fuel pressure (without running it) seems to come right up to 31 when the pump primes and slowly falls off again. I had let it sit for a full 30 minutes and it dropped down to 16 PSI at that point. Still uncertain about the spike in pressure when depressing the throttle and how that relates to the sputter and stall. Is that flooding the engine? Would that imply my injectors are shot/shoddy?"

Sounds like the check valve in the fuel pump fuel return line is leaking. It should hold 29-31 PSI after power on cycle. The Fuel pressure regulator is operated by engine vacuum. But if it holds 31 psi for a minute or 2 after powering on the ignition switch (do not start, just turn power on and watch the FP pressure for 1-2 minutes), it does not sound like the current problem.

But if it is leaking down slowly to 16 psi in 30 minutes it may be a clue that it has trash in the check valve, or the seal is going bad, and that the leak down rate might be worse at times, one of those issues that comes and goes! I call it a hit and run gremlin! Gotta watch constantly for them as they like to hit and run, leaving few clues as to who they were, where they came from, or where they went and when they will return!:laugh: I forget if the FP regulator is part of that check valve on the Renix???? I think HO has the check valve in the fuel pump, in the tank. Renix may be using the Fuel Pressure regulator for the check valve as well as the pressure regulation. I don't recall right now for sure.

It is normal for fuel pressure to spike during acceleration for a second. Also normal for it drop a little, like to 29 during rapid deceleration.


"I know, I'm going to be told to get a noid light -- and I'm not sure what that is, but I'll just hope it's not a joke to make the parts guy look at me funny. Only noid I'm familiar with was on dominos commercials in the 80's..."

Noid lights:

http://www.google.com/search?q=noid...s=org.mozilla:en-US:official&client=firefox-a

But when you check out, be sure to ask if Snipe are in season yet! LOL:laugh:

box_goblin said:

Renix sensor readings forthcoming -- once I get it running again.

Took the fuel pressure test; 30-31 PSI while running at idle - disconnecting the vacuum from the regulator shoots it up to 38-39; so that seems right on spec.

Decided to see what it did while opening the throttle; with slow, gradual opening it stayed fairly steady at 31. if I opened the throttle more quickly -- the engine stuttered as expected, and the PSI kicked up over 40. I released the throttle and the engine and fuel pressure quickly returned to normal. I repeated it, but held the throttle open this time -- not all the way to WOT -- and it stutters and sputtered and died.

It has now returned to the state of cranking the engine with no start/catch (sputtered once or twice but that was it); exactly like it was before. Does this sound like a fuel delivery problem, or is that kind of fuel pressure fluctuation normal/okay?

Back out to take sensor readings....

Click to expand...

It should peak at 39, not "up over 40". So how far up over 40 did it go?

Check and make sure there is no gasoline coming out of the vacuum connection on the FPR. If the diaphragm goes bad on the FPR, the vacuum line will suck extra gas into the engine.

"TPS: Supply 5V
closed: 0.65 V (seems low?)
WOT: 4.3V
Increase from closed to WOT seems pretty smooth, but I only have a digital MM, so that's from what I can see there."

.65 at idle is way too low. Needs to be .82 IIRC.

Click to expand...

Okay -- I'll see if I can't figure out how that adjustment process works for this guy and get it adjusted properly; could this being out of adjustment cause the stalling?

"I also noticed that my "ballast resistor" (didn't know what that thing was previously) was no longer on the bulkhead by the egr; but laying down below it. Taped together. That an issue; or is it fine as is?"

Depends on what tapped together means? The ballast is bypassed while starting, used to slow the pump while engine is running. It basically gives the fuel pump full battery power while the engine is cranking as the battery drops to about 10 V while cranking. Then with engine running, alternator running the battery is up to 14 volts, so the B.Resistor drops the voltage to the fuel pump to about 12 V to extend the FP life.

Click to expand...

TAPED -- not TAPPED; as in, held into one piece with tape. The top half appears to have broken off of it.

"Fuel pressure (without running it) seems to come right up to 31 when the pump primes and slowly falls off again. I had let it sit for a full 30 minutes and it dropped down to 16 PSI at that point. Still uncertain about the spike in pressure when depressing the throttle and how that relates to the sputter and stall. Is that flooding the engine? Would that imply my injectors are shot/shoddy?"

Sounds like the check valve in the fuel pump fuel return line is leaking. It should hold 29-31 PSI after power on cycle. The Fuel pressure regulator is operated by engine vacuum. But if it holds 31 psi for a minute or 2 after powering on the ignition switch (do not start, just turn power on and watch the FP pressure for 1-2 minutes), it does not sound like the current problem.

But if it is leaking down slowly to 16 psi in 30 minutes it may be a clue that it has trash in the check valve, or the seal is going bad, and that the leak down rate might be worse at times, one of those issues that comes and goes! I call it a hit and run gremlin! Gotta watch constantly for them as they like to hit and run, leaving few clues as to who they were, where they came from, or where they went and when they will return!:laugh: I forget if the FP regulator is part of that check valve on the Renix???? I think HO has the check valve in the fuel pump, in the tank. Renix may be using the Fuel Pressure regulator for the check valve as well as the pressure regulation. I don't recall right now for sure.

It is normal for fuel pressure to spike during acceleration for a second. Also normal for it drop a little, like to 29 during rapid deceleration.

Click to expand...

I wasn't clear here, I don't think. The pressure doesn't drop off WHILE it is running; that's after 30 minutes of sitting. I was attempting that leak down test -- I think what I saw looks like it is in line with what it should do. I didn't do any of that pinching off business as the pressure seemed to sit within acceptable limits -- right on really; unless that spike when the quickly opening the thottle is not normal. If anyone can tell me for sure that is normal that would help me out a lot. I can't quite get it started back up again now; it was close...so very close...just didn't catch...

Ecomike said:

It should peak at 39, not "up over 40". So how far up over 40 did it go?

Check and make sure there is no gasoline coming out of the vacuum connection on the FPR. If the diaphragm goes bad on the FPR, the vacuum line will suck extra gas into the engine.

Click to expand...

Went back out; Fuel pressure gauge I'd left attached to the rail was reading dead 0. Now that I think back, when I attached it, nothing spurted at all, and I think it read 0 then too...
Got it to start (Engine cranking and sputtering for 5+ seconds, like it was out of gas...then finally caught).
After letting it idle for a little while, I pushed the throttle watching the gauge - the peak is right up at 40; it does not go above that.
Checked the vacuum line coming off the regulator again; gives same 8 PSI spike when not attached; no evidence of gas coming out of there, or having had come out of there in the past (no odor or wetness at all) and fuel pressure stays right at 39 -- even when I do the throttle push test. It still sputters like hell, but the fuel pressure stays at 39 (so that must be where it is spiking when the vacuum is attached? it is quick so it is hard to get a balls on accurate reading, but that looks pretty damn close if not exactly the same spot.)

I have it off, and am checking the pressure leak down again -- it dropped to 28 almost immediately after the engine was turned off this round.

Sounds like the FPR and fuel pump are all working fine.

Yes, the .63 TPS at idle is low enough to cause it to die. The ECU is extremely sensitive to that voltage reading at idle. At .63 it is telling the ECU to idle at about 200 rpm or less.

That ballast resistor sounds worrisome. I think disconnected, it should be about 2.2 ohms. But if it was bad, you would not have good fuel pressure.

In the mean time, this gremlin has reinfected my 89 jeep!:banghead:

After prolonged testing and intermittent starting; I decided to clean up the cable contacts on all of my plug wires.

While doing so, I noticed that the wire connecting coil to dist was "loose" at the point where the contact with the coil was made. Swapped a cable from a plug into there and viola.

I haven't had a chance to drive it to where it was failing previously -- hot, at freeway speeds, etc -- but every other little thing that was running poorly has gone away by changing out that plug wire with a new one.

Apparently the wire/contact on that cable is loose, no longer giving a clean, 100% connection. Bugger me that it would work every time I tested it previously -- glad I decided to put some of that dielectric grease I'd be reading about on things....