Engine surge

Idle surge in a diesel could be due to advanced timing." you have a bad stepper motor (controls the injection advance) on the injection pump located on the left front, don't worry dear item only $500

I'm not sure I understand the mode of failure with the stepper motor you described. Are you saying the injection timing stepper motor is "up stepping" momentarily then correcting itself by "down stepping" to its normal position without any pulses from the PCM? Also would a change in timing cause such a high variation in RPM without an increase of injected fuel volume?

You will need to have a scanner to verify exactly what the timing is at before start up and during idling if you do not have access to a scanner it is going to be very difficult to determine the variation in timing.

I have a scanner and had it connected for some timewhile driving and idling without an occurrence of the problem. The other day while leaving a parking lot and starting the engine the momentary high surge in engine RPM occurred(no scanner attached at the time). By high RPM I mean a very short duration of approximate 1500 to 2000 RPM; like depressing the accelerator pedal. It seems like the occurrence of the problem is considerably less in cold weather.

hook your scanner back up go to the timing section and tell me where the timing is set at, with the vehicle not running, and with the vehicle running.

Dr. Loot
I'm not sure how to get the timing info you suggested. I hooked up my scanner engine off key on but did not get any timing info or didn't know how to access it. Any help on how to access it would be greatly appreciated.

I would love to help you fix it I have done to many of these, do you have a scanner?

Thanks, I'll have to ask around. Meanwhile what are your expectations relating to timing in my situation?

all I know is that's where you start, when you have the symptoms you are describing.

Do you know if Auto Zone or Advanced auto parts would have the more sophisticated scanner to get the timing data? Also having limited experience with diesels, it's hard for me to understand how timing variations without additional injection volume could give such a large difference in RPM. I thought that injection advance was relative to increased RPM due to latency fuel burn time. However if you have experienced the problem, I'm all ears.
Thanks

for example a gas engine if you twist distributor advancing the engine, the engine RPM will increase. on your specific application the timing is control by the computer, which uses the stepper motor to control the timing, if the computer loses its parameters within the timing specifications, the engine will idle and run erratic

When you say erratic, are you saying a significant amount of RPM change?

yes, up and down

I've timed many a gas engine and I'm aware of the RPM changes as you vary the timing however in the case of my diesel, it's more like someone momentarily depressed the accelerator pedal. Suprisingly, I have not had a single occurrence in the past few weeks or more. Maybe it's temperature related. It's been cold.
Still trying to locate someone with a Snap-on scanner.

send me your e-mail address I need to send you some photos that this site will not allow to download, wrong program

i recently was running codes for bank 1,2 running lean and my engine started acting up it would surge. it sounded like it was going to shut off. my engine light went off and the truck is still doing it. i have the 5.3 v8. my question is what could it be that would be causing this? it is getting worse now. could it be fuel pump? cracked intake manifold? intake manifold gasket? please give me some input thanks

If you have a lean mixture, it could be many things. I would start by looking for vacuum leaks. Check all hoses and the intake for leaks.

Let me know what you find.

Joe

i work at a lg chevy dlr and therefore feel weird as oking for help here but they have been chasing this problem for a month and it is costing me a fortune in guesses. They just repl my intake man gskt due to leaking and overheating. Since then my truck will surge and buck and has died on 2 occassions. it only happens sometimes. we have replaced plugs, wires, cap and rotor. Yesterday while acting up it set the ck eng lite and the code was mass air flow sensor which we replaced and still messed up. Is there something that could have been loosened or a wire pinched when the intake was done?

This may sound foolish but have they check it over carefully for any intake snorkels or breather tubes that may be left off or leaking? Have you tried cleaning the MAF.

I would try replacing the coil, or coils. I had a similar problem with an '02 V6 camaro. The cat converter went bad, causing engine and underhood temps to rise. Once warned up, the engine misfired, hesitated like you wouldn't believe. I replaced the MAF, plugs, wires, filters, and fluids. After I replaced the converter, I still had the problem. Problem went away after I replaced 2 out of the 3 ignition coils. The computer won't tell you if the coils are bad, no trouble codes for that, only 'misfire'. Could be ignition module, but I would go for that last. Coils can be cheap on ebay, that's where I got mine. Also check all wiring to the ignition module and coil(s). Also check crank trigger sensor, especially if it is the type that bolts onto the frame and it is a rod that points to the harmonic balancer. If it is damaged, your ignition system is junk.

While coils are a common cause of misfire on DIS ignitions systems, they are not with distributor ignition.
I wouldn't recommend throwing any more parts at it or buying anything from E-Bay. Most of it is Chinese junk that didn't sell at the flea market.

au contraire, mein fruend,

I had a '96 Cheyene (Silverado) with a coil problem.
Turns out there was a wire that was fraying that was going to the coil (I suspect a signaling lead) that was causing my engine to die when I took a hard turn. It had a distributor and a single coil. True, the coil itself wasn't bad, but it was part of the ignition system.

I just bought 3 new coils for my '02 V6 Camaro, I've had them on for about 3 months, and they have worked flawlessly so far. I know that my original coils barely lasted 80,000 miles, which I think is a JOKE in this century. I didn't see anything on these coils that suggested it was built in China, but anything is possible. Even HD gets stuff made there now, I'm sorry to say. What can you do??

[quote:b34f3ef414="02redcamaro"]au contraire, mein fruend,

I had a '96 Cheyene (Silverado) with a coil problem.
Turns out there was a wire that was fraying that was going to the coil (I suspect a signaling lead) that was causing my engine to die when I took a hard turn. It had a distributor and a single coil. True, the coil itself wasn't bad, but it was part of the ignition system.
[/quote:b34f3ef414]

So, how in your mind does a frayed wire translate into replacing coils to fix that problem. As I said, a single coil isn't going to cause a misfire. PS, the issue you were having was a breakdown of the primary ignition signal and not actually what is considered a misfire.

the truck surges betwee 40 and 60 mphs any ideas what might be wrong?

What I'm saying is that I think it is possible that you have some kind of coil-related problem. If you have a single coil, then I would focus on any connections to that coil if it is a misfire. That could be primary signal lead, wire to distributor, distributor cap, rotor,
perhaps even ignition module. If you have a multiple coil system, one or more coils could go bad (as in my case), causing misfires (trouble codes said misfire).
Could be plug wires or plugs, they would be easy and cheap to try first. The computer, unfortunately,
isn't very good at focusing a misfire problem towards an individual component.

Do you have a check engine light and when was the last tune-up?

Possibilities here could be one of the following below:

could be caused by one of the following below

Oxygen sensor.
Catalytic converter.
Fuel injectors dirty/sticking.
Mass airflow sensor/Airflow meter.
Throttle position sensor.
Crankshaft position sensor
Knock sensor
Manifold absolute pressure sensor.
EGR Valve
Fuel pressure regulator leaking or defective fuel pump.
Fuel contamination.
Foul/defective spark plugs.
Open spark plug wires.
Ignition coil/Coil packs defective.
Incorrect ignition timing.
Cap and rotor.

Note:If it doesn't apply disregard it and keep testing.

Try turning off the overdrive. You should have either a button or shift it from D4 to D3. It could be a TCC solenoid kicking in and out.

we just purchased the truck for my son.not sure when the last tune up was but the guy we got the truc from kept it well maintained and yes ther is a check engine light on replace the up and down stream egr`s passenger side light went off for a few hundred miles and came back on