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Tool Hut
Tool Hut, ASE Certified Technician
Category: Chevy
Satisfied Customers: 494
Experience:  Owner of a mobile diagnostics company assisting auto technicians with difficult vehicles
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Timing doesn Timing doesn't advance much when Black/tan wire

Customer Question

Customer: Timing doesn Timing doesn't advance much when Black/tan wire re-attached. 1988 chevy 4.3L
JA: Thanks. Can you give me any more details about your issue?
Customer: I worked with one of your folks last year on this issue, and it did not get resolved. Symptoms improved but never solved. Engine Hesitation after warn-up
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Submitted: 11 months ago.
Category: Chevy
Customer: replied 11 months ago.
Fuel Pump + sending unit in tank replaced last year which helped some, but not entirely. Over the course of this past year, symptoms have gotten worse again, so I replaced the Fuel pump again, and symptoms improved but not eliminated again. I read somewhere to use only AC Delco pump, so that is what I installed. I also pressurized the return line and EFE line to be sure no leaks were present . There could have been a leak in the EFE line near the tank connection, but that was taken care of. The vapor canister was also replaced, as well as almost everything else on this vehicle, and no change. The vehicle has had this issue for well over 6 years.
Expert:  Roy replied 11 months ago.

good morning my name is ***** ***** I will assist

as far as the timing, when you re connect the timing wire with engine running, the timing does not change until you turn it off and re start. then the timing should go back to the control of the ignition module.

have you had the timing chain checked for slack??? this will cause your hesitation

Roy

Customer: replied 11 months ago.
Hi Roy,
I will go through a list of a few items replaced.
- Timing chain & Sprockets were replaced 3,000 miles ago
- Serpentine Belt recently replaced
- Entire throttle body was replaced with Brand New Holley direct replacement ($600.00 + dollars)
- Distributor replaced with new from Summit
- Spark Plug wires replaced
- New EGR valve
- Several ECM's plus new remanf unit from Advance Auto
Customer: replied 11 months ago.
A key indicator that might be giving me a clue
- Runs fine cold
Customer: replied 11 months ago.
I'm open to replacing items, as I know new items can be bad as well.
My next step was to replace the oxy sensor, but this is a shot in the dark
Several TPS sensors already replaced and since new Holley throttle body I assume this should be fine
Expert:  Roy replied 11 months ago.

ok, good information thanks

as far as the cold running, that is controlled by the ect. that is a temp sensor that sends the temp to the ecm which adjusts fuel mixture. that in itself could be a problem as they were common failures along with the connector in the past.

did you ever check the actual fuel pressure??

Roy

no, O2 sensor will not do it. it would code if there was an issue

same with tps. it sounds like you have a basic engine issue at this point.

Roy

Customer: replied 11 months ago.
Fuel pressure was checked several times, it appeared within range, although I had a question regarding when the ignition was turned off, pressure dropped quickly. However the tech I spoke with last year indicated this should be normal for this vehicle. Is that true?
Expert:  Roy replied 11 months ago.

no, it should retain some pressure for the next start up.

what was the actual pressure??

Roy

Customer: replied 11 months ago.
Also I have an Auto X-Ray tool and I have monitored the coolant temp, and it increases and decreases fairly well with the engine running.
Customer: replied 11 months ago.
I'll need to recheck pressure
Customer: replied 11 months ago.
I haven't checked the pressure since the new pump was installed a couple of days ago
Customer: replied 11 months ago.
Pressure what I remember with the old pump was around 12 psi, but that is going from memory
Customer: replied 11 months ago.
One other point, engine starts very quickly. Even after a quick turn off
Expert:  Roy replied 11 months ago.

12 lbs is good. with key off, it should be around 4-5 lbs.

how high does the temp go when hot???

Roy

Customer: replied 11 months ago.
I haven't checked the max temp, but I can check that very easily
Expert:  Roy replied 11 months ago.

the hooter the temp shows, the leaner the ecm will make the engine run

Roy

Customer: replied 11 months ago.
I can check the engine temp . Although the engine never overheated, and nothing brought high temp to my awareness, I can still check that item.
Should that be the next step? Should I then get back to you ?
Expert:  Roy replied 11 months ago.

yes, check the temp when the motor is hot.

Roy

Customer: replied 11 months ago.
How do I get back to you ?
Expert:  Roy replied 11 months ago.

you can log back in and continue

Roy

Customer: replied 11 months ago.
ok - thank you, I just saw a parallel response in my inbox.Also enjoy & have a good holiday
Expert:  Roy replied 11 months ago.

thanks. please dont forget to rate me as it is the only way I get paid for my efforts

Roy

Expert:  Roy replied 11 months ago.

thanks. please dont forget to rate me as it is the only way I get paid for my efforts

Roy

Customer: replied 11 months ago.
Hi Roy,You were asking the max temperature the vehicle reaches. Here's what I can provide based on the diagnostic tool I used.
The engine closed the loop at 90 degrees F
The Max temperature reached by the engine was roughly 188 - 190 degrees F.
Additional information that might help
Knock Sensor steady at 28 counts
Integrator fluctuated 127 - 131
Mixture changed frequently between rich and lean
O2 cross counts changed once per second.
MAP sensor in park @ idle = 1.15 to 1.29Also there is a slight (very slight) roughness to the engine at idle. This is not observed once the engine gets to approx. 1200 rpm.This problem has perplexed me for years so hopefully you have something else for me to check .
Expert:  Roy replied 11 months ago.

all those readings look good. it looks like it could be a mechanical problem, not a control problem.

I would start by removing the valve covers and watching the rocker arm movement while running to see if one may not be moving the same as the others

Roy

Expert:  Roy replied 11 months ago.

please dont forget to rate me as it is the only way I get paid for my efforts

Roy

Customer: replied 11 months ago.
Hi Roy, I haven't had a chance to check the valve timing / lift yet. Hopefully this weekend. Also want to mention, approx. 4,000 miles ago I took the heads off, cleaned them and re-assembled. The r & r was strictly to clean the heads and replace the valve stem seals, due to oil smoke on an overnight start.
Expert:  Roy replied 11 months ago.

ok, let me know

Customer: replied 11 months ago.
Roy, Here's what I can tell you after removing the valve covers
- All valves appear to be moving up and down the same amount. ( I did not put a dial indication on the valve to check lift though) .
- Valve lash was set to 0 plus 1 turn, so this was backed out, so now it is 0 plus 3/4 turn.
- Oil was noticed trickling down each valve rocker arm and valve spring. However something interesting was spotted. Each valve rocker /spring had oil trickling as mentioned, however number 4 intake had a stream of oil surging through the top of the pushrod. The oil was pumping so much more than the others that it was squirting beyond the head casting by a small amount.
Does this signify a problem with intake #4, or perhaps the other valves not pumping enough? Could this suggest a problem which could result in the slight engine hesitation ?
Expert:  Roy replied 11 months ago.

you can even back off the valves to 0 plus 1/2 turn. it will give you better low end performance.

all valves should have good oil pressure through the push rods. how many miles on this motor???

Roy

Customer: replied 11 months ago.
This is a re-manufactured motor, from Budget Engine Rebuilders in Cleveland, I installed 12 years ago.
Since the install, the motor has accumulated approx. 48,000 miles.
Expert:  Roy replied 11 months ago.

have you ever done a compression test???

Roy

Customer: replied 11 months ago.
A couple of years ago I had done a compression test, and all seemed reasonable at that time. But I will check again, and let you know the outcome. Might be a few days, since it appears winter finally took a foothold today.
Expert:  Roy replied 11 months ago.

ok

Customer: replied 10 months ago.
Roy, Here's the results of the compression test. Also all 6 spark plugs were carboned-up after 9 months and 250 miles. The carbon was dry... no oil present.
#1 128 psi
#2 129 psi
#3 130 psi
#4 130 psi
#5 130 psi
#6 131 psi
Expert:  Roy replied 10 months ago.

back to your original question, does the timing advance with the connector attached??

Roy

Customer: replied 10 months ago.
When the connector is removed the timing drops to 1 degree. I know it should be zero, but it appears to run better the further advance I manually set it.
Re-attaching the connector, the timing does not re-advance until I turn the vehicle off and then back on, as you indicated earlier. Then it sits at approx. 16 degree advance when warm and at idle.
Revving the engine, further advances the timing another 6 degrees (maybe 22 total). However if I quickly peg the accelerator arm from idle, the timing briefly drops to 0 degrees (100msecs maybe), then jumps back to 16 degrees & then ramps up from there.
These readings were when the vehicle was warm, but not driven, as it is parked in the driveway for now. I can only assume that if put on the road, would continue to have that slight bogging affect while accelerating
Customer: replied 10 months ago.
I guess my question is whether this appears to be normal timing advance? If normal, what else could cause this bogging effect.
Expert:  Roy replied 10 months ago.

yes, that is normal. but the dropping to 0 concerns me. I suspect the ignition module not working correctly.

Roy

Customer: replied 10 months ago.
100 msec might actually be longer than what's happening,. But it is long enough for the eye to catch it. I can try another new ignition module and retest if you think it is worthwhile.
Expert:  Roy replied 10 months ago.

yes, I think thats a good idea. that is what controls the timing.

Roy

thanks. please dont forget to rate me as it is the only way I get paid for my efforts

Roy

Customer: replied 10 months ago.
Roy, I thought the policy of Just Answers was that I would pay a one time $26.00 fee if satisfied with the service I was provided with the question I posed? Although I am happy thus far with the response of your answers, the problem is not any further along than when I started. Now I received a second bill of $26.00 and some type of membership. What's the deal?
I had planned on committing to the initial $26.00 at some point regardless, but even the first $26.00 I never yet committed to.
Expert:  Tool Hut replied 10 months ago.

Hi, My Name is ***** ***** for posting your question to just answer. I am a independent contractor for just answer, and ASE Certified Master Auto Technician with 20 years experience. I am confident we can resolve your problem together.Please remember I don't know your skill level. I can't see, smell, hear, or touch the vehicle. It may take a few back and forth replies to get to a satisfactory resolution.There will probably be some equipment needed for a proper diagnosis. If you are not comfortable with this or do not have any test equipment please let me know ASAP. I also try to give all of the information you may need expecting a positive rating. I am not compensated for my time until you leave a positive rating. Your rating should be based on the service you received.

Do you still need help?

I have attached a picture of a knock module, I just need to know if your vehicle has this module. It is next to the throttle body on a bracket.