I've recently had problems with my truck sputtering, cutting out and pinging. It usually does it after about 25-30 mins. of hyw driving and is most noticable when I have my foot in it. It usually starts cutting out at about 3500 rpms and eventually works its way down to 2500 as it continues. Of course, going down the hyw I am often in 4th or 5th at 2500. I lose speed to keep my foot out of it to control the missing so that my driveline doesnt take a beating. The tachometer responds and fluctuates between actual/desired rpm to low very rapidly, like as quick as you could shut the truck off (tach fluctuations are not smooth). This indicates to me (along with the pinging) that the problem is in the ignition system. as I think fuel problems would result in fluid fluctuations of the tach. Out of gear, it idles fine and the sputtering is evident only if you rap it back out above 2500. This may carry on for 5-10 minutes and then subside somewhat, but it can get to where I have to exit the hwy because I cant keep up.

I cant say that the problem is consistent, only that I only have problems after the the truck warms up and humidity plays no role.

Also, the other day it up and died in McDonalds drive-thru. That is the limit for me, when I cant get a %#@ hamburger without my truck dieing Im not a happy camper. When I turned it over it would just crank and every 4 or 5 turns of the key it would start for a second and shut off like I turned the key back off. After attempting to start if about 15 times half the McDonalds staff helped me push my truck out of the middle of the hamurger lane. I played with the coil, ignition and tach wire to attempt to find any loose connections. After another 5 minutes the truck finally started with hesitation but my fiddling seemed to make no difference. I then drove home and ate my cold hamburger and fries. (I wont cuss.... I wont cuss.... I wont cuss..)

%$#@!!!!!!!

This has gone too far.

Distrubutor, ignition module, coil cap and rotor are all 2 months old. Plugs and wires are 1 month old. I have attempted to keep all spark plug wires seperate despite the excess smog &*$@ on my truck (Cali emmis. legal maybe?).

Can timing problems cause this? It doesnt happen all the time, so I didnt think so.

What about a component getting hot, ie coil, ignition module etc. Anybody heard of this causing problems?

Any other ideas?

Sorry about the long post.

I hate it when I cant trust my truck. All I want is a #!@$& hamburger.

 

A bad coil can cause sputtering at high rpms but it usually won't cause pinging. Sounds to me like it could be an EGR problem.

-Jon

 

Get your EGR valve checked out and make sure they check where it dumps into the intake manifold . It can crud up there . Mine did

 

Pardon my ignorance, but what does the EGR have to do with it? I mean I have a vague idea of what it does, but I don't know how it can cause the engine to cut out.

 

What year is it and is it Mass-Air or Speed Density.. assuming your TFI module truly is GOOD (Because that is what it sounds like to me).. then if it were a mass-air truck I'd try swapping w/ someone but first and foremost I'd be pulling codes. A bad TPS could cause some of this, bad coil.. did you do ANY changes just before it started?

EGR: when the exhaust gas is recirculated it dilutes your intake charge mixture so the timing is advanced and it could ping if the EGR is not working but the timing advances anyway..


Just reread your post: fuel pump. Do you have dual tanks? Does it only happen when you are running one of the tanks? Some year trucks had a pump in each tank. Other years had a helper pump in the tank but the main pump (single) was externally mounted on the chassis. If you have no codes and this problem persists, its probably your fuel pump. Hook up a fuel pressure gauge to that thing and hang it out the hood so you can see it. I'll bet $ that the fuel pressure is dropping below 30psi..

 

If all else fails, ditto on the fuel pump. I have two tanks with a pump in each one. Earlier this year while on a trip, my motor was cutting out at high RPM's while climbing a steep hill, revving around 3k RPM. Strange, I thought. Did it again on the next hill. So I switched to the front tank. While merging on the freeway, I ran it all the way up to 4500 RPM, and it ran flawless.

A couple weeks later the fuel pump just quit pumping.

 

I thought about the fuel pressure, I'm not sure it would cause such drastic fluctuations in the tach. The tach will drop 1000-1500 RPM's with the truck locked in gear (manual tranny) without a drastic change in speed. This would mean a drastic drop in spark without a drastic drop in engine RPM's. To me it just doesnt make sense. Pinging with loss of spark. Am I right here? Maybe Im wrong on the loss of spark, just seems that way.

I'm gonna read the codes tomorrow night and if that doesnt show anything I'll break out the fuel pressure gage. I dont think it is long enough as it is to get it outside the hood so Ill have to figure something out. It will cut out even if I get off the hyw and rev the engine up so maybe I can just do that. I have dual tanks with the rail mounted pump also, but unfortunately my back tank sprung a leak and I havent got a new tank installed, so I cant switch tanks. I suppose a clogged pickup screen could do it too (filter is only a couple months old as well). Pressure test will tell anyways. I'm also gonna make sure the plug wires are seperated enough, plugs and wires was the most recent thing I did.

While the coil, distributor, TFI module, wires, plugs and TPS are new (all within a couple months), I've had new parts go bad before so who's to say. Just cant replace everything since its not running right though.

Its an '89 S.D. (see my sig on original post)

 

Well Ive narrowed it down to the fuel pressure regulater. Fuel pressure is 35psi KOEO and only 30PSI EO Disconecting the vaccuum from the regulator yeilds 40 psi EO. Parts run tomorrow evening after work.

Thanks guys.

I only hope that I didnt hurt my top end too much, I wanted to put off my header/cam/big valve pocket ported heads until I had a little more money.