# VG30i running badly



## BitterDave (Feb 24, 2011)

Hi guys,

First time posting here and I need some help. Sorry about the legnthy post, but I'm trying to include as much detail as possible.

I've got a 1986.5 D21 with the VG30i (throttle body injection) engine and 285k miles on it. Several months ago I started having intermittent problems where the truck would start up just fine, but then stall almost immediately. Keeping the throttle open would only keep the engine turning at a low, stumbling RPM for a little bit before eventually stalling. This happened a few times, but the rest of the time the engine ran fine.

A few weeks went by and everything was fine until I started to lose power (over a 20 second time span) and was forced to pull over. After that I couldn't get the engine to run. It would start, but stumble at a low RPM and then stall. I had it towed to a mechanic where _new_ Nissan fuel injectors were installed ($600 just in parts!). The truck would start again, but ran like crap (very rich and hesitation). I doubled checked the work and found that the mechanic didn't seal the the area were the fuel injector wires exited the housing. I put some RTV there and everything ran fine for two days... 

Until my truck started to loose power again yesterday after driving for 40 minutes. I noticed that the idle was a little low. I would gently accelerate and after a second or two the RPM would drop down to a low, stumbling idle. Adding more throttle wouldn't make much of a difference, but then all of a sudden the power/RPM would come back for a few seconds and accelerate me forward, before resuming the low RPM again. In neutral I would try to maintain 2000 RPM, but after a few seconds it would drop to idle again.

I pulled the codes and it shows 33, which is the O2 sensor, but I doubt that's the problem, more likely a symptom. I believe that the ECU runs in an open loop for the first 20 seconds and I still get the problems within those 20 seconds.

Other interesting discoveries:
- Pulling the fuel pump fuse doesn't actually cut power to the pump. It used to work, but now now. Haven't look into this yet, but I don't see how this could be related.
- I was getting error code 13, cylinder head temp sensor, but it turned out to be a bad connection and is now fixed.
- I don't see the correct voltage at the diagnostic port (near the fuse box) for my fuel mixture heater, but I tested the voltage/resistance at the heater and it looks ok.
- When the idle was running low, there was a strong gas smell. I'm thinking that maybe I'm not getting a strong spark???

Any ideas would be greatly appreciated. Thanks.


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## steve cassel (May 25, 2011)

Dave, Just ran across your thread and I'm wondering if you ever got an answer? I'm having the same problems and symptoms you described on my 1989 D21 truck. I see there were no responses to your thread, but I'm hoping you managed to solve the problem... (I'm hoping it's the O2 sensor). 
Steve.


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## BitterDave (Feb 24, 2011)

Hi Steve,

It turned out the be a bad/dirty connector for the throttle position sensor (near the engine). Mechanic cleaned it up and it's been running fine since.


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## CMax03 (Jan 17, 2009)

I would remove and reinstall those injectors with new orings ...... and check all your lines for tightness with no leaks!


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## BSERIES18C407 (Mar 17, 2020)

BitterDave said:


> Hi guys,
> 
> First time posting here and I need some help. Sorry about the legnthy post, but I'm trying to include as much detail as possible.
> 
> ...


Hey dave, been awhile since last came on, at that time was having similar problems as your issues, sorry about nobody responded immediately to your questions but this forum is decent with helpful information, glad you fixed your truck as i having injector circuit issues that after almost 1yr of trouble shooting and to no end and after injectors,ecu, tbi rebuild,fuel pump replacement it ended with weber carb conversion and that ended the injector (limp mode) issues not reving past 2300rpm, however carburetored there's no issues to worry in regards to tps,injector and other sensors involved.


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