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Hesitation, then dies upon acceleration


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I thought I had this issue resolved like 3 times now.  Still reoccurs.  This last time, it took 2-days for the symptoms to reappear.  I thought I had it.  Nope.

 

I'm now on my second thoroughly cleaned throttle body (TB) to try to correct this.  I had broken some TPS/IAC studs on the first one and just wanted to replace the whole TB anyway.  Also, I've used a different  (used) TPS and AIC on the second TB.  I indexed the butterfly plate inside the TB (set-screw) as recommended and I've properly set the TPS with my multimeter per well documented instructions.

 

Here's the symptoms:  Seems to be too low rpm, at least to my ears.  Both TBs that were installed seemed to be low rpm as a matter of fact.  Engine often dies once acceleration begins, say at a stop light for instance.  When it dies, I have to quickly shift into park and start again, of course.  Sometimes, I have to wait a second before restarting, as the starter system appears completely dead when I turn the key.  It has always started back up when this odd event happens.  I often get a surge of rpm when it restarts.  Idle seems a bit better with this second throttle body, but again seems like rpm seems to be too low by my ears.  By better, I mean is sounds more consistent and not missing so much.  But I do slightly detect that it doesn't seem perfect.

 

I've performed Cruiser54's tips 1, 18, 28, 29.  Automatic/column shift transmission, by the way.  

 

Based on what I'm reading about the CPS here on the forum, it appears to not be associated with my symptoms.  

 

As soon as I get some time, I plan on continuing with Cruiser's electrical cleaning tips.  I have a third used IAC that I haven't yet tried, so perhaps I just have two bad IACs, though probably unlikely.

 

Am I missing a critical troubleshooting tip? 

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2 minutes ago, Ωhm said:

Since this is a new thread and to save a re-reading of older threads, exactly what parts were loaded into the "parts cannon" over the past year?

 

I've had the truck only for 6-Months.  No real parts cannon for this particular problem, other that what I noted above that you read:  a different cleaned and indexed TB with a different set of IAC/TPS.

 

Once possible clue:  I had to replace my fuel tank.  When I took my truck bed off, I discovered that that tank was badly corroded.  Upon reassembly, I did have to FOREVER crank the engine to get it to fire for the first time with the new tank and new fuel filter.  I did drizzle a little fuel into my TB intake hose to assist.  I initially figured that I may had fouled the TB and that's why I concentrated my efforts on it and it's components.   Two cleaned and indexed TBs and little results so far.  It's improved but still the low rpm and sporadic dying is there. 

 

Typical "tune up" items replaced since ownership:  wires, AC plugs, Dist cap, etc.

 

Had future plans on upgrading to 4-hole injectors, but not in the budget yet.  That sounds like a parts cannon response, but again, I had plans on doing it anyway.  Sure would like to know what's up with this and to see if I can correct it before I dump funds in injectors.

 

Besides IAC, what negatively affects rpm and bogging upon acceleration?  Can I correctly boost rpm in some way just to see if this corrects the stalling?

 

 

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Renix uses CPS (engine RPM's), TPS (throttle position) and MAP (engine load) for fuel mapping strategy (INJ PW). IAC will hunt and search for desired RPM's if one or more of these sensors fail or are intermittent. O2 will add or subtract time from the injectors, if needed. These are your major driveability components. All of these are parts cannon ammo. P/N can add RPM's (≈50) when vehicle is put in gear. Check this by seeing if vehicle starts in gear. Take cautions here. Also when vehicle dies on the road use N for your restart.

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On 1/14/2018 at 12:34 PM, Ωhm said:

Check this by seeing if vehicle starts in gear. Take cautions here.

No quite tracking you here. What exactly am I checking by doing this?  It will not start in D, by the way.

 

There were times in traffic that it did not start in N, but then again I was quite stressed to get the dang thing running quickly.  I know it starts in P, but sometimes after a few seconds.  

 

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Starter Relay coil finds a path to ground through the NSS (P/N) switch allowing the starter to engage, so does ECU_pin_C4. ECU_pin_C4 (labeled Start Signal (-)) tells the ECU vehicle is not in gear since it also finds a path to ground. When ECU_pin_C4 is open from ground the ECU will allow for idle speed compensation (kick +50 rpms). If vehicle had started in gear, allowing both starter to engage and ECU_pin_C4 to find ground (No rpm kicker). Starting in gear usually occurs when someone has bypass the NSS or a short to ground on NSS circuit. Clear as mud, right?

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3 hours ago, Ωhm said:

Starter Relay coil finds a path to ground through the NSS (P/N) switch allowing the starter to engage, so does ECU_pin_C4. ECU_pin_C4 (labeled Start Signal (-)) tells the ECU vehicle is not in gear since it also finds a path to ground. When ECU_pin_C4 is open from ground the ECU will allow for idle speed compensation (kick +50 rpms). If vehicle had started in gear, allowing both starter to engage and ECU_pin_C4 to find ground (No rpm kicker). Starting in gear usually occurs when someone has bypass the NSS or a short to ground on NSS circuit. Clear as mud, right?

 

Took 6 times to read it, but I think its sinking in.  So, the search continues since NSS circuit appears good.  

 

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  • 3 weeks later...

 

Some significant changes, but still have idle issues, low rpm and the engine still dies often at stop lights.  

 

New 4-hole 746 injectors installed.  New Mopar TPS installed today. New lifetime warrantied CPS installed last week--I did Cruiser54's advance mod on it and opened up the top mounting hole to get it a bit closer to the flywheel.

 

New killer primo distributor cap with the brass contacts installed last week.  

 

I tested MAP last week, but had no vacuum guage/pump to really do it justice.  I used my lungs to check for voltage variances.  It seemed to be ok, but obviously the test without a vacuum pump tool ain't gonna be 100%.  Today, I got the vacuum tool from AutoZone and I'll do it right tomorrow.

 

I also picked up a fuel pressure test kit from Autozone.  I'll have to figure out how to use it, but I think I read that I probably should check fuel rail pressure for my troubleshooting this problem.

 

On 1/14/2018 at 1:06 PM, cruiser54 said:

Tip 5 could diagnose the problem......

I'm going to try Cruiser54's Tip 5, although I did already check the TPS for good ground when I put it on.  Maybe somewhere else in that harness is giving me fits.

 

On 1/14/2018 at 12:34 PM, Ωhm said:

O2 will add or subtract time from the injectors, if needed

I also plan to muiltimeter check O2 sensor tomorrow, but I want to go ahead and order a new NGK one anyhow.  I'm sure this is probably the original one I have on there.   I have just over 120K miles I think.  Even if the O2 test passes, I assume that the performance of my sensor likely degraded over the past 29-years.

 

 

On 1/14/2018 at 12:34 PM, Ωhm said:

IAC will hunt and search for desired RPM's if one or more of these sensors fail or are intermitten

I've had three different stock IACs on there with no change for my problem.  This thing is still dying at most stop lights and has a very low idle while stopped and in drive.  I am hearing deviation in idle speed and general behavior, so I think that's probably what is happening--IAC is searching.  

 

I read that EGR is operational only really at acceleration?  So a bad EGR shouldn't effect anything at idle, right?  Would bypassing it temporarily help with this diagnosis at all?

 

Besides my continuing troubleshooting plan for tomorrow, does anything else come to mind to help me out here?

 

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Performed Cruiser54's Tip 5, checking for bad grounds throughout the harness.  Set my multimeter to Ohms 20.  Set black probe to battery NEG and my red probe to TPS wire B.  It pulled a .50 the whole time I wiggled the main wiring harness.  GROUNDS GOOD.

 

Did fuel pressure check.  Was running 32psi during idle and it jumped to 39psi when I disconnected VAC tube to regulator.  Pressure bled down pretty good after I shut engine off (to about 20psi in about 20-minutes) but I think my fitting wasn't so secure.  Wasn't too worried, as my engine has always started promptly.  Probably the rental pressure gauge fitting.  FUEL PRESSURE GOOD.

 

Completely tested MAP with a vacuum pump/guage.  Input/output voltage with key on tested fine.  Output voltages tested fine as well as I presented various stages of vacuum.   MAP GOOD.      

 

I sprayed carb cleaner along vacuum lines and especially at joint and fittings.  Appears to have no vacuum leaks.

 

I'm going to go ahead and replace my O2 sensor with a good NTK. From what I read, testing requires more work to find anything close to accurate troubleshooting for a 28-year old original O2 sensor than is worth.  Another interesting thing I read:  An exhaust leak from a cracked header or a very leaky downpipe connection (in which I have) can cause poor O2 sensor input to the system.  I'll tighten my leaky downpipe, replace O2 and hope this fixes my problems.

 

Still anxious to hear if EGR needs to be looked at that my be causing my issues.  Can I just pop and plug the vacuum line somewhere to quickly eliminate it as a culprit?

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17 minutes ago, Ωhm said:

EGR has no bearing on engine idle on less EGR valve is stuck open or partially open. Yes, pop and plug the source vacuum line at the EGR solenoid to disable EGR.

 

Thank you very much for the response, Sir.  We'll try that.

 

Beginning to run out of ideas, I'm afraid.  Ordered a NGT O2 sensor and NGK copper plugs today.  We'll try that next weekend when they arrive.  Good Lord, I hope that's it.

 

I did find #1 spark plug wire occasionally arcing outside the boot to the head.  Pulled the wire and found what appears to be corrosion on the metal clip that grips the spark plug.  This is a 4-Month old set of wires.  Anyhow I cleaned it all up, Oxyguarded the metal, used di-electric on inside of boot and reinstalled with wire dryer spray afterwards.  I suppose I didn't quite have it secured on the plug maybe.

 

...I can't help but remember how the rpm and idle was good prior to me pulling the bed and replacing the new tank and fuel filter.  I think I screwed something up between that and the hour-long cranking of the engine to get it to start after getting it all back together.

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I also read that loosened intake bolts may cause these type of issues.  I'll snug them tight tonight when i get home.

 

I document my trials and errors here and ask questions not only in the hopes that i can fix my problem, but also to benefit the next poor soul that has similar issues.  I have read many previous posts relating to this issue and many simply seemed to have dropped off and become inactive without the original poster identifying how he found the solution.  

 

I sure want this issue to have a happy ending because right now I can't help but feel that disappointment creeping in that I jumped into this unique world of MJ ownership.

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  • 1 month later...

So today I can finally say that my hesitation/idle issues are resolved.  In case you're having similar issues and are now reading this, here's the solution that corrected my issues.

 

It was one or doing all of the below things:

1.  Welded mildly cracked header and closed the very bad leak at the collector pipe.  I also welded a small gusset between the last two exhaust pipes of the header for added strength, by the way.

2.  Replaced my O2 sensor.

3.  Replaced my water temperature sensor (the one down towards the bottom of the block, driver's side).

4.  Eliminated my EGR.  Did this while I had my header off.  Removed tube connecting header to intake/EGR.  Sealed with weld.  Cut off EGR diaphram and other parts from it's cast iron housing.  Replaced iron housing with sheetmetal sandwiched between it and the intake manifold.  

 

My guess on which had the most likely impact would probably be the O2 sensor replacement but I'm only guessing.  I had to do all of this together at once, so I didn't have the opportunity to try each individually to test each one.  Maybe a combination of them all, who knows.  

 

Hope you find your solution and I hope my case can help you.  

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8 hours ago, omega_rugal said:

you did all at once, now we will never know what was the real issue...

The thanks I get....  I'm so sorry i wasted your time, Sir. 

 

Surely someone, some day, will actually read this thread all the way through and PERHAPS get something out of it.    

 

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3 minutes ago, coolwind57 said:

The thanks I get....  I'm so sorry i wasted your time, Sir. 

 

Surely someone, some day, will actually read this thread all the way through and PERHAPS get something out of it.    

 

I'm just glad you got it fixed!!

 

It could have been a combination of all those things you did. some folks want a silver bullet cure handed to them.......

 

I commend your diligence in taking the bull by the horns and doing something rather than pissing and moaning expecting someone to provide the silver bullet. 

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