Engine/Transmission (1994 - 1998) Motor cutting out under hard acceleration

[DMC]

I have searched the boards for any info on this and have'nt found anything that really describes what my problem is. So here goes.



Today I had the overdrive turned off as it will make the truck more responsive in stop and go traffic. Well I decided to stand on it to blow out a little carbon. Well it accelerated quite well up until the motor hit around 2500 rpms and then it jerked violently until I let off. This very much disturbed me as it could do damage to the drive line. I've never had this problem before and can't recall ever trying to run the rpms to red line with overdrive off. The truck ran up to about 85 mph with my foot in it in overdrive, and as long as I kept my foot in it, it was smoking somewhat. So it is getting fuel.



Maybe the rev-limiter scenario applies here, as I have read where some have cut the white and orange wire going to the PCM.



Has anyone got any ideas?





Thanks for the help



Don

 

[chrleb1]

If it was putting out some white smoke at the same time, it could have been your timing. If too low (timing), and lots of fuel, it could pop and jerk.

 

[Deezul1]

Unless auto trans trucks are way different there is no electric type rev limiter. Its all mechanical inside the injection pump. May have a governor spring problem but thats a wild guess.

 

[DMC]

When I was having the jerking fit there was no white smoke. That was with the overdrive locked out. I rarely hammer on it with the overdrive locked out, I just normally run the rpms up to around 2000-2200 then reengauge the overdrive. When I gouged on it with it in overdrive it would black smoke some. But its always done that since I turned the starwheel on the afc forward about 20 clicks. When I get on it hard it will in most cases black smoke and then clear up. If it is not the governor then I'm wondering if it might be the TPS? I think I will run the rpms up to the max tomorrow slowly with the overdrive locked out and see what happens. Maybe by then someone that has had this happen will read this thread and maybe know of the cause.



Thanks



Don

 

[jtwcummins]

Sure sounds like the guv is cutting off fuel. Try winding out w/OD off and not hammered. See where the fuel starts cutting out. Mine did this until I got 3k springs. My guess is not under hard accel cutoff should happen about 2700 rpm, something about getting on it causes cutoff to happen about 200-300 rpm lower.

 

[Howard Durand]

Could that possibly be the torque converter lockup doing funny things?

 

[DMC]

well I went out and gradually ran the RPMS up to 2500=2600 with no problems. I couldn't go any higher than that due to the available roadway. I'll mess around with it a bit more when I get a chance to put it on the interstate.



Thanks fo the feed back





Don

 

[DavidGardner]

Don

Had a friend with a 96 auto with the TST 230/605 plate. One day it started to act up when he got on it to pass. Rough running loss of power and lots of white smoke. Driving around normaly no problems. Turns out he had installed an after market fuel filter pre stock fuel filter that had plugged up. The canister on this filter was clear plastic and it looked clean as a whistle. Changed the filter and problem went away. Would be worth a check to see if your fuel filter might be going south.



Good luck and let us know what you find.

Dave Gardner.

 

[JohnE]

overflow valve

Have you checked fuel pressure or replaced the overflow valve.

Without good fuel pressure the injection pump doesn't work as efficient especially when you push the rpms.



I agree with chrleb1 on timing.

My truck also smoked at higher rpm after I installed 3k governor springs but hadn't advanced the timing. Bumped timing to around 16-17&deg and it really drives nice. Of course, the #4 plate makes it smoke a bit, too.

 

[DMC]

Well I went out and slowly ran the rpms up with the overdrive locked out. And it fell on its face at about 2700 rpms. I guess that is the governor cutting off the fuel. I just didn'y think it would be so abrubt when it defuels. I used to drive longhaul semi's and when you would bump the governor it was not jerky like it is with my truck. I guess its time for the spring kit. As far as fuel starvation is considered I think I'm getting plenty of fuel, it pulls real strong up to 2700 rpm. It also pulls really well in overdrive. I change the fleetguard fuel filter every 10,000 mi. Have a new overflow valve and fuel lines, and lift pump.



I wonder if I can adjust the governor springs enough to get me to 2950 - 3000 rpms.



Thanks for the help



Don

 

[jtwcummins]

2700 rpm is right where the auto gov shuts off fuel, it is not a smooth deal either, especially when on it hard. If you know someone with the manual trans who has put 4k springs in you can put those in and get close to 3k rpm. They also don't jerk when fuel is shutdown, alot of stock manuals get 3000 rpm plus with the factory springs. The fact you can get to cutoff not floored usually means there is plenty of fuel, but springs are a little weak.



When you change the fuel filter make a 50-50 mix of ATF and fuel. ATF burns okay and is high detergent, keeps things from getting coated with the stuff from fuel.

 

[DMC]

Thanks for the help guys, I'll check my manual for a breakdown of the p-7100 and see about getting some higher rpm springs for it.



I really would be interested in reading more about the procedure for changing the governor springs.



Thanks Again



Don

 

[Howard Durand]

It seems strange that it only happens with the OD locked out.

It would be interesting to see what would happen if you could manually lock up the TC before you hit the max rpm.

I am thinking your TPS could be sending some crazy signals at full throttle.

 

[DMC]

Howard I agree with your thoughts on the tps. I was thinking about going and finding a place to wind her out with the overdrive engauged. I will be doing in excess of 110 mph before I test the upper limits of the governor. I'm seriously considering picking up some 3000 - 3500 rpm governor springs.



Thanks



Don

 

[paulsmith]

My 96 did the same thing, VIOLENT shut off when locked out of OD. I normally lock out OD on the on ramps when pulling a load, and I swear I think I bent my frame when it bucks at 2500 while pulling. I mean scary! The orginal poster knows what I mean!



I bought a DTT trans, and installed the 3 k governor kit, and it no longer does it. I can tell you, I suspect the transmission was at fault. What ever it is, it is not normal fuel cut out. Mine did it for over a year, through several fuel filters, fuel presure checks, etc.

 

[DMC]

Paulsmith:



I certainly do know what you mean. Its not a good feeling at all. You think that something has just broken and you see $$$$$ for a second and it stops and it does it again. This all happens in about a second under hard acceleration around 2800 rpm. I've been thinking about the 3k gov spring kit, I think I'll get those for when I slide my cam plate.



Glad you got yours in there, now you can wind her up a bit without worrying about that gut wrenching jerk fit.



Thanks



Don