Renix issue?

[5-90]

If you're looking for a flat spot in the TPS, you're not going to read voltages. That's a secondary measurement usually used to check adjustment of the thing.

You want to grab an analogue ohmmeter (one with a sweep needle,) and check for actual changes in the resistance of the thing while you're moving the sensor's lever. The reason for using an analogue meter is simple - digital meters have buffer circuits built into them that delay readings, and you'll get a 'false fail' from using a digital.

When checking for a flat spot, absolute readings are not important. What you're looking for is a smooth change in resistance that paces along with the motion of the sensor's lever - if it hitches, skips, or sticks; you're looking for a replacement sensor.

 

[jujuscisyn]

yes, I was probing voltages with a digital before throwing the analog on it.

 

[jujuscisyn]

ruled out the tps. when it comes to temp even at idle the rpms drop from 600-700 down to below 500. Try to give it gas and it stumbles and pops. Any ideas folks? I still have vacuum issues to resolve but it only gives me fits at 210 degrees. The electric fan kicks on at around 220 and runs for a bout a minute and a half. I really appreciate the help. If its not heat soak could it be a plugged cat. I only have one o2 sensor as it is a 90 and that ohms out. Granted I know that only checks the heating element.

 

[BillDunn83]

i have the same issue with mine but it doesn't happen as much as yours.. mine only happens every few weeks. I went to NACfest last weekend, went wheeling all day long and didnt have a problem but driving to my girls house 15 min away it is spitting and sputtering on me. seems to be after going up long hills at highway speed. anything you find out please share the wealth and I will do the same..

 

[jujuscisyn]

Not to worry, I fully plan to. Right now everything is suspect. Ohm'd out the MAT this evening and appears to be in specs gonna check it again after it cools down and see if the resistance goes up(it should) checked the CTS as well again gotta wait for the jeep to cool down to check again. I've heard of the coil getting hot and causing these symptoms, I'll have to check. Had it for a year now and has done it the whole time and I have no idea of its maintenance history but I am slowly but surely starting a new one. Good luck with yours, if you find something out before I do, I'd be very interested in the info.

 

[stealth919]

my dad 2000 chevy was doing this and i found the problem to be the fuel pres regulater. it was leaking fuel back through the vacuem hose that hooks to it in the manifold. once it sat it bled fuel in the intake aaaa

 

[stealth919]

and causing a rich stumbling start but when you held the throttle body open when starting it did great pulled the vac hose off and hadfuel pouring out. might help

 

[Ecomike]

ruled out the tps. when it comes to temp even at idle the rpms drop from 600-700 down to below 500. Try to give it gas and it stumbles and pops. Any ideas folks? I still have vacuum issues to resolve but it only gives me fits at 210 degrees. The electric fan kicks on at around 220 and runs for a bout a minute and a half. I really appreciate the help. If its not heat soak could it be a plugged cat. I only have one o2 sensor as it is a 90 and that ohms out. Granted I know that only checks the heating element.

Still sounds like a TPS issue to me. Perhaps the TPS to ECU wire path is compromised. Try disconnecting the TPS and see if you have the same stumble problem, but wait, yes a clogged exhaust "cat" could do that too. Check the FPR too.

 

[jujuscisyn]

Thanks alot folks, i'm held up with daddy duties today but I'll check them as soon as possible and let you know what I find out.

 

[winterbeater]

Test for clogged cat is to hook vacuum gage up to intake manifold, start engine, watch for steady decline of vacuum as cat backs up exhaust.

 

[jujuscisyn]

Just an update: Haven't got a lot done on the thing, found a very bad vacuum leak from TB to Map. Repaired that and thought I had it whipped...guess not. Drove it today, 190 to 210 degrees and got a stumble. Its not poppin and backfiring quite so bad but just a few here and there. Still ohming out connectors and wires. Thought I'd let you know since you've all been so good about the help.

 

[jujuscisyn]

Double checked the CTS and MAT sensor and both appear to be ok but while I was at it I checked the CPS(crank position sensor) and it ohmed out at 265 ohms and was steadily falling. This was after I had let it cool down to about 120-150 degrees to test the other two sensors. Could this be a thermal failure on the CPS. The renix fuel injection manual says 200 ohms +/-75. It doesn't say to check it hot or cold. If it was 10 ohms from being out of spec at 135 degrees or so could warming it up more push it out of specs and would that cause the stumbling and backfiring?
You guys have been a big help thus far and can't thank you enough. Next on the list the fpr. I'll test that everywhich way I can think of.

 

[Ecomike]

Double checked the CTS and MAT sensor and both appear to be ok but while I was at it I checked the CPS(crank position sensor) and it ohmed out at 265 ohms and was steadily falling. This was after I had let it cool down to about 120-150 degrees to test the other two sensors. Could this be a thermal failure on the CPS. The renix fuel injection manual says 200 ohms +/-75. It doesn't say to check it hot or cold. If it was 10 ohms from being out of spec at 135 degrees or so could warming it up more push it out of specs and would that cause the stumbling and backfiring?
You guys have been a big help thus far and can't thank you enough. Next on the list the fpr. I'll test that everywhich way I can think of.

You need to get up to the failure temperature (210 F ) and then retest the CPS to see if gets way out of spec then. I would say 300 Ohms is still OK (as meter error could be 20 more ohms), but you might find it at 500 ohms, which is bad once it gets good and hot.

 

[winterbeater]

Or pour water on the CKP (CPS) to see if it clears up the problem. (After it is missing when hot)

 

[5-90]

You need to get up to the failure temperature (210 F ) and then retest the CPS to see if gets way out of spec then. I would say 300 Ohms is still OK (as meter error could be 20 more ohms), but you might find it at 500 ohms, which is bad once it gets good and hot.

Which is why I keep a cheap hairdryer in the bottom drawer of my toolbox - it helps to diagnose heat-related failures...

 

[jujuscisyn]

Man am I ready to pull my hair out. Got it hot, checked CPS and it ohms out at 273 ohms and falling after shutdown. So I doubt its that. Pulled the plugs and it looks like someone rolled them in a bag of charcoal. This is 2days after seafoam. Which may be a bad o2 sensor but definately rich. I'm running out of ideas. The next thing to do is start throwing parts at it and I most definately can't afford that. Did notice an intermittent fuel leak on the fuel rail at the in port gonna have to put an o ring in that. I don't know, the way it hesitates, pops and bucks it sounds lean but the plugs say rich. Gonna keep working on it.

 

[xjtrailrider]

Have you checked the EGR? I would make a block off plate to go between the EGR valve and intake(sandwiched by 2 gaskets) and see how it runs with out the EGR. Use a gasket as a template and cut the plate out of some sheet metal.

The EGR was most of the issue with my RENIX besides ground issues and I was able to tweek injector timing some by cranking the dizzy around a few degrees but thats another issue.

 

[jujuscisyn]

Thanks for the input, Haven't done the egr delete per se, I have cut and plugged the vacuum line between the transducer and the valve. Preventing the valve from opening except maybe with a huge amount of exhaust pressure. Not sure if thats correct but thats what I've done. Did notice that when you give it sudden throttle there is a huge hesitation no matter the temp.

 

[Nickfast]

Really sounds like vacuum leak to me.
Have you checked your intake manifold bolts? Run a propane torch (not lit) around all possible areas of the engine while idling and see if the idle picks up/smooths out.

Nick

 

[Ecomike]

ruled out the tps. when it comes to temp even at idle the rpms drop from 600-700 down to below 500. Try to give it gas and it stumbles and pops. Any ideas folks? I still have vacuum issues to resolve but it only gives me fits at 210 degrees. The electric fan kicks on at around 220 and runs for a bout a minute and a half. I really appreciate the help. If its not heat soak could it be a plugged cat. I only have one o2 sensor as it is a 90 and that ohms out. Granted I know that only checks the heating element.

How did you rule out the tps? Did you check for noisy spots when it is hot using the analog meter method?

Have you considered or tested the O2 sensor?

Have you checked for I-E manifold leaks, loose bolts?