'89 rebuild, idles fine but sputters at RPM

Hey y'all,
I posted this question to the pirate board and someone suggested I try here, so here it goes.

I rebuilt the 4.0 in my 89 Laredo. It's back in, started up fine once I made sure the fuel line was all the way on the fuel rail, and it idles fine. Problem is, if I give it any gas it sputters and can't make its mind up on whether it's going to die or not. I'm not getting any power, just getting over the little bump into and out of my shop is a challenge.

Here's what I've checked so far:
Dist: Rotor is just to the left of the #1 post at TDC 0.
CPS: Measures 223 ohms. Appears to be bolted tight, but will double check tonight. Wire harness is good.
New plug wires, new cap. Will get new plugs today (but the ones in the rig really should be fine, they were when I checked them during the rebuild).
No Cat in the system, 2.25 through a Magnaflow (I think).
No check engine light.

Possibilities:
Fuel: 3/4 tank of gas is 9 mos old...definite possibility, but remember, it idles fine, so I would think this would preclude a fuel quality problem? Wouldn't a fuel quality problem be more intermittant? I put some heet in there a few days ago. Haven't changed the filter or pump, I'm gonna pick up a filter today. Draining the tank would be a real PIA due to it being over 3/4...
Knock sensor is broken and not installed, but again, this would be an occasional pinging type of deal, not a constant sputter, wouldn't it?

Any other ideas? I need to break it in this week because I have to drive to Idaho next week. (Yea, I know. I'm a week behind my original timetable.)

Thanks!

Try checking your fuel pressure, vaccume lines, and I've had a similar problem with my IAC, you can pull it out of the throttle body, and with throttle body cleaner, clean it off.
I had an IAC that was really dirty and i had a similar problem.

Also make sure the TPS is adjusted correctly

Sounds kind of like a MAP sensor it will/can idle OK (but rich), if you throttle up any the engine just kind of sputters and acts like it wants to die.
Make sure the vacuum line to the MAP isn't broken and you don't have the rubber plug at the TB, the vacuum line goes into, upside down. One of the (twin) holes for the plug is a blind hole (bottom I think). I occasionally disconnect the MAP vacuum line and blow through it checking for constriction.
I glued the rubber stopper into my TB with a little silicon. I occasionally poke something into the hole at the base of the TB to make sure the orifice is clean or blow on the MAP end of the vacuum line, with it plugged into the TB base.

Make sure the electrical connector for the MAP is oil free and clean. If all else fails, double check the harness plugs near the firewall. There are two that can be switched, if your in a hurry and muscle brain them together. The last time my MAP was acting up it was a bent pin at a harness connector.

You sounded like you were pretty careful about TDC, but the motor can idle well and run bad if the rotor is a tooth or two off. Maybe double check your TDC. Try one tooth counter clockwise and see if that helps.
It's been awhile, but I sure don't remember the rotor being after "1" in the original setup.

Thanks for the tip, more for my growing list of items to check tonight. The book wasn't all that specific about indexing the dist, however the consensus of what I've read here and at the pirate board is the trailing edge of the rotor should be .20 advanced of the #1 post. Ha, the book says "5 O'clock." Wow, big help there. Anyway, Thanks!

I'll second the dist being one tooth off.....happened to me when I dropped in a rebuilt motor even after I was very careful to index it.

Wilfite said:

Thanks for the tip, more for my growing list of items to check tonight. The book wasn't all that specific about indexing the dist, however the consensus of what I've read here and at the pirate board is the trailing edge of the rotor should be .20 advanced of the #1 post. Ha, the book says "5 O'clock." Wow, big help there. Anyway, Thanks!

Click to expand...

When your indexing for an after market cam (or worn distributor gears) you cut the aligning slot (ears) off and set it up 0.020 after the "1" pole on the distributor cap. The OEM initial setup, the rotor is retarded quit a bit (from the 0.020 setup). I seem to remember it being somewhere *before* the *center* of the rotor contact reaches the "1" pole on the cap (It's definitely not 0.020 after), if memory serves me right the leading edge of the rotor contact just makes it to the "1" pole (or there abouts) at TDC with the OEM setup.
I always (repeat always) put the motor at TDC (align the timing marks), mark the outside of the distributor case with a crayon and reinstall it the same way it came out. In fact I keep a bottle of day glow orange finger nail polish in my tool box, I mark everything.

Here is a link to the setup for an HO. The best I recollect they go in the same way, so likely the measurements for the HO are applicable for the Renix also.

Thanks for the info, that's different from what I've heard, it's worth a try. I didn't see the link you mentioned in your post, however. I didn't get much done tonight, it's about 25 degrees outside and fuel lines don't like to move in this weather. I'll try it again after work tomorrow.

Another thing, I noticed tonight my fuel send to the fuel rail doesn't fit well on the rail's nipple. I put a new quick-connect on it, but it's loose and I can smell fuel. Obviously can't drive it that way, do I need to get a new flexible hose, or could I have somehow broken the quick-connect setup?

1. Check ALL of your vaccumm stuff. There is not much. One cracked or loose connection and you will have this problem. There is a couple of stems on top of your intake manifold going to the brakes, to the valve cover, and to your air box and charcoal canister.
Get a fuel pressure guage from HF, about $15 or $20
On the fuel rail there is a valve that looks like a tire stem valve on the fuel rail.
Put the fuel pressure guage on it. I believe with key on it should be 35 or 40psi
Engine running about 30-35
Turn the engine off and do a leak down test (watch to see if it drops pressure quickly.
This will eliminate the fuel problem,
If it passes the fuel test, mine has the problem with the CPS connector. I have to pull mine apart and spray it with electrical cleaner and put it back together. This is really sensitive connection, some guys have to solder the connectors to solve it. CPS is usually works/doesnt work, but has a lot to do with my high speed sputter at 3000 rpms when warm.

Check your coil, you can remove it and take it to Vato Zone to test it.

And I have used gas that is two or more years old and it worked find...

Get the sets of torques threads 1/4 drive type sockets to pull the throttle body (get your gasket ahead of time.

i really dont like the quick connectors.

there are two small o rings inside an they are prone on older vehicles to tear or get misaligned during installation.

mine was actually leaking out of the crimped side, went to a wrecking yard to get another peice.....just to find out that from the intake back to the gas tank the fuel line is one piece.

aside from that the only one i could find was on a commanche which wouldnt have worked anyway. so i cut the metal tube and just flared it and spliced it to my existing line.

that crimp leaked also....

now i'm running a fuel line with the crimped end cut off and a hose clamp.

havent had a leak since.

and in regards to the distributor.

i'm having a similar problem

i've got an aftermarket cam and everything's put together.

i'm simply going to cut the tabs off so i can adjust it manually, as i have an external hold down also. would i be able to put a timing light on it and tell when i'm advanced or retarded the right amount?


i know the computer will compensate for some of this, should i just turn it untill the computer is satisfied? i should be able to move it to a point where its close enough for the computer to hold it where it needs to be, and with a timing light i would be able to notice that regardless of moving the distributor back and forth the timing wouldnt change.


correct?

wingnutooa said:

and in regards to the distributor.

i'm having a similar problem

i've got an aftermarket cam and everything's put together.

i'm simply going to cut the tabs off so i can adjust it manually, as i have an external hold down also. would i be able to put a timing light on it and tell when i'm advanced or retarded the right amount?


i know the computer will compensate for some of this, should i just turn it untill the computer is satisfied? i should be able to move it to a point where its close enough for the computer to hold it where it needs to be, and with a timing light i would be able to notice that regardless of moving the distributor back and forth the timing wouldnt change.


correct?

Click to expand...

A timing light isn't going to be any help at all.

Cutting the tabs off!!! First you do the standard factory setup, **then** with the cut ears,you turn the distributor until it is 0.020 after the "1* pole on the cap. In effect advancing the initial timing. Doing the initial setup at the 0.020 point (slipping a tooth) actually retards the initial timing.
I think the problem is mostly in the semantics (language). I've had my distributor out and in dozens of times and never had any of the problems you guys seem to be having. Idles like a champ, never misses a beat, accelerates like a rabbit, obvious whatever I'm doing works. The problem is likely my poor ability to explain it.
If it wasn't 15 deg outside, I'd set up TDC "1" and take some pictures. Half hour process max.
The computer is going to compensate up until about one tooth off, usually rather well, 2 teeth off will cause grief. There is a rather wide envelope/or window were the timing (ECU) adjusts itself.
One trouble spot is the contact of the rotor is so darned wide it is easy to get a tooth off aiming for number "1" pole on the cap.
There may be a flaw in my reasoning, but it's hard to argue with good running results. Even if I'm doing it wrong it works well.
It's been mentioned here that the computer compensates, the compensation is an envelope. I'm guessing here, but it seems likely that cutting the tabs (ears) and doing the setup at .020 after "1" pole on the distributor moves the envelope more towards the ideal center, so you don't run out of possible advance/retard options (moves/adjusts the envelope).
Indexing to 0.020 after is mostly unnecessary, many of the 87's needed this adjustment, after that they fixed the flaw. An aftermarket cam or excessively worn gear teeth can cause the envelope to shift some.

OK, stupid question time. It's early, you'll have to put up with me.

What are you using for your "aiming point"? The leading edge, center or trailing edge of the rotor blade?

You have to keep the tabs ( or ears) fairly aligned (eyeall) with the hold down bolt hole to get this to work. Oil pump/distributor alignment can also make the process last a few tries.

The finished product, the rotor blade center should be close to the "1" pole (mark the side of the distributor housing). Or very near half way between the cap hold down screw holes (on the side the harness exits), with the tabs and the hold down bolt hole aligned.
I really can't remember of the rotor blade center ends up slightly after (which seems likely) or slightly before the "1" mark on my housing. If you are off a tooth the difference is the full rotor blade width and more, you'll notice.
Most caps are marked "1" on the top, some aren't.

wingnutooa said:

and in regards to the distributor.

i'm having a similar problem

i've got an aftermarket cam and everything's put together.

i'm simply going to cut the tabs off so i can adjust it manually, as i have an external hold down also. would i be able to put a timing light on it and tell when i'm advanced or retarded the right amount?


i know the computer will compensate for some of this, should i just turn it untill the computer is satisfied? i should be able to move it to a point where its close enough for the computer to hold it where it needs to be, and with a timing light i would be able to notice that regardless of moving the distributor back and forth the timing wouldnt change.


correct?

Click to expand...

OK, I backed up a tooth and couldn't start, so went back to where it was before, roughly 5:30ish. I guess that's the right spot. It'll start but still sputters when I give it gas. I have to head back to work, will pick up a new CPS later (grrrr...) and try that.

Wilfite said:

OK, I backed up a tooth and couldn't start, so went back to where it was before, roughly 5:30ish. I guess that's the right spot. It'll start but still sputters when I give it gas. I have to head back to work, will pick up a new CPS later (grrrr...) and try that.

Click to expand...

Not so quick with the CPS - did you check the fuel system? Pressure and flow? 2 other posts suggested this along with qualifying vacuum lines.

A guy went through the same thing awhile back, I really can't remember what the post was called. He forgot and left his grounds loose after a motor rebuild. I forget which, the head to firewall ground or the battery to dipstick mount ground.

thanks . will try this later.

in the mean time just picked up a 92 limited for 500 bucks.

sweet!!!

can you reference that picture with all the small writing?

tried printing it and it was too blury to read.

where did you get it?

or can you enlarge and repost?