RRC idle problem, stall on acceleration

[agbuckle98]

1990 RRC idles very low, eventually stalls. Also hesitates badly when starting from a stop, once above about 1200 RPM, it will pull like nothing was ever wrong. Idle problem started while wheeling today, temps were 85 - 90, engine very hot, aux fans and clutch fan engaged almost all day. 2 hour highway trip home was perfect, but stalled at the end of the exit ramp, and bogged down badly trying to accelerate. no codes on the underseat box, but does show 02 after reconnecting the battery. any suggestions on the best ammo for the parts shotgun?

 

[gabriellaconi]

Check the timming. Make sure its 6 BTD. Also, you said you went wheeling. Any wather? If so, check the MAF sensor. Once i got this thing wet, and the iddle was low and erratic, it even stalled a coulple of times. This would display a code thou...

 

[agbuckle98]

no water on this trip. The next day I drove it to work, truck ran perfectly fine until it was warmed up, then the stumbling idle and bogging to get going. Once over 1500, it is perfect.

 

[rover4x4]

Do the O2 sensors and new plugs

 

[agbuckle98]

O2 sensors have been replaced within the year as have plugs wires, cap and rotor. After doing more searching here and other sources I decided to replace the coolant temp sensor, and did a flush at the same time. Things are 90% better. The same problem is still there, but it has much less effect on the truck now. It hasn't stalled all week, but will still bog down slightly when coming off idle, and will start to idle rough if sitting at a light too long. I did swap out the idle motor for a new one I had sitting around and cleaned the idle passages as well, no change at all.

 

[agbuckle98]

:banghead: This is what I've been doing all day on my day off with the RRC. Here is a list of parts I have swapped from my Bro's good running '91 RRC:

MAF - no change
TPS - no change
Ignition coil - no change

I've also checked spark at all 8 cylinders, it's good everywhere. there are no vacuum leaks, timing is rock steady, the Vac advance does work. FPR seems to be working, but hard to tell as there is no pressure tap on the rail of this truck. The idle does bump up when I disconnect the vac line to the FPR, and will actually sit and run fairly well with the small vacuum leak and the pressure bumped up.

 

[lforgue8]

how old is the ign module? and is the ign module remotely mounted if not now is the time to do it....also how long since you repl the fuel filter?

i had the same problem long ago when i first put my truck on the road and chased EVERYTHING in the ign sys and fuel sys...

those 2 things were what got me back going

 

[92rrrandall]

The poor idle AND hesitation pulling away from stop is most likely caused by a leaky intake hose. The worse the leaks, the worse the effects. Once you get moving good the leaky intake hose will have minimal effect. Codes throw will be 44, 45 and 48.

Part# ESR1611L or make one up from a 3" 45degree tube and two pieces of 3" silicone tube.

Randall

 

[lforgue8]

i totally forgot about the "t" piece....vacuum leaks are i thought just the first thing you check...oh well

hey randall...can you pm me on those ecm chips you burn

 

[agbuckle98]

no vacuum leaks anywhere, and no codes thrown at all. In desperation I tried something that that I was sure wasn't going to work, but a buddy of mine would not SHUT UP untill I tried it. Got a can of GM top engine cleaner. Now this stuff is meant for carb engines so it is just a spray can with no hose or anything. I sprayed the entire can into the plenum where the t piece hooks up, keeping the revs around 2000, the engine choking and putting up a fuss the entire time. When the can was done, I shut it off and let the truck sit for 20 min. Started it back up, blew smoke everywhere, ran it around for 20 minutes, it has run perfectly ever since. That was 4 days ago, it has only bobbled the idle once or twice since then, never stalled, and takes off from a stop smooth as can be. I'm still scratching my head.........

 

[singingcamel]

Clean your tps and your throttle body just for good measure..

 

[agbuckle98]

problems have resurfaced, but present differently now. For the most part, the truck runs perfectly, but will stumble and die occasionally. It will do it at idle, and will also put up a fuss while driving at slow street speeds (15 - 20 mph) Happens mostly when cold and during the warm up process. I can't nail down if it is a fuel or ignition problem. I am leaning toward a fuel issue. I have been testing the ignition with a timing light on the coil wire, and the light doesn't cut out when the engine stumbles. The problem seems to come and go so fast I have to think it is an electrical issue somewhere.

 

[rover4x4]

How old is the alternator?

 

[agbuckle98]

How old is the alternator?

amazingly, the alternator is original to the truck (at least as long as I have owned the truck) but has never given me problems, always charges at 13.9v, never more, never less. Tell me you're going somewhere with this, I'm wiling to try anything!

 

[agbuckle98]

BTW, the stumbling / cutting out problem has no pattern anymore, it seems so random, and presents itself in many ways as well. The only constant I can come up with is it will NOT give me problems under hard acceleration.

 

[agbuckle98]

Finally threw out a code 12. I have fiddled with the MAF earlier in the saga, even swapped out for other units, but I guess I will re-visit that area and report back.

 

[agbuckle98]

regarding the earlier post about the alternator, can an old alternator possibly be creating some kind of electronic noise that could affect the MAF operation? Are they that sensitive?

 

[ptschram]

Base idle might be worth revisiting.

 

[agbuckle98]

Base idle might be worth revisiting.

I'me sure it couldn't hurt, but for the most part, it idles fine, then will throw a fit and stumble, sometimes stall, and still has issues with light throttle at low speeds. Cleaning the MAF in response to the code 12 did nothing, nor did trying the swap again. I'm still not 100% sure if it's a fuel issue or a spark issue. When it starts to act up, it never pops or backfires through the intake like these things seem to like to do, just dies out smoothly.

 

[singingcamel]

Any news on the fix ?