Rough Idle - problem solved

[YukonGTmaster]

Dear all,

thanks a lot for these valuable pieces of information. This is highly appreciated.

I was able to crank the engine manually by using an extension bar for my ratchet. I am pretty sure I cranked it over to TDC of cylinder #1. My old rotor pointed then to #1 cylinder (not to #8).
Unfortunately, I didn´t mark anything because I only read your advice, especially the one of "east 302", only afterwards.

Please take a look at the pictures:

1) Did I really find #1 TDC? Isn't this a strange mark on the pulley? I carefully inserted a screwdriver into the bore of my spark plug and found that the piston is almost at one level of my spark plug hole.

2) Is the newly installed distributor pointing into the correct position (#1 TDC)? I think it is a little bit too far off its intended position (clockwise).


I tried to start my engine but now, it won't crank easily. It feels like as if the battery is low. So I charged it again (fully charged) but same effect. It feels as if the is too much compression and it only started for a moment still running rough, stalls and then didn't start again. Is it possible that I brought in another fault with my new distributor? Is it possible that the converter is clogged because too much unburnt fuel is now inside?

I wondered why the compression test for cylinder #5 was so high (17 bar)? Was too much fuel inside the cylinder at the time of testing?


I am really looking forward for some advice again. The Tahoe here is quite rare and so it is hard to find a good garage.


Best whishes
Falco

View attachment 279180 View attachment 279181

That mark does not look like the TDC groove on your harmonic balancer. It should be a defined machined groove perpendicular to the balancer wheel. That mark you have it aligned to, looks very suspect. Note the mark on the attached picture. I would pull your belt off and rotate the balancer clockwise 360 degrees and look with a bright light.

 

[BG1988]

Yes! Remove the serpentine belt before turning the crank with a socket and ratchet.

you can manually crank it by pressing the starter relay

 

[exp500]

BG1988- Please post a pic of said relay on this vintage! Sauce or it doesn't exist!

 

[BG1988]

BG1988- Please post a pic of said relay on this vintage! Sauce or it doesn't exist!

the old mechanics trick was to squeeze the relay for the starter to manually crank it


why not use the key? and pull the fuel pump fuse

 

[willxfs]

Kowalski,

It really sounds like you set your distributor with No. 1 cylinder at TDC on the exhaust stroke not the compression stroke. To set the timing correctly, No. 1 cylinder need to be at TDC on the compression stroke. The easiest way to identify if you are on the compression stroke is to have someone put their finger over the spark plug hole of No. 1 cylinder while you turn the crank with your ratchet. As the No. 1 cylinder is coming up on the compression stroke, the pressure will try to push your friends finger off the hole. It will be very noticeable. You will also notice that the machined groove on the balancer will line up with the V shaped marker on the timing cover. Good luck.

 

[Kowalski]

I used a wrong mark on my pulley - you were all right. So yesterday, I found the correct mark and was able to install my new distributor correctly.

But still, it is idling rough with strong smell of unburnt gas. I then disconnected the mass airflow sensor and it then ran smooth! Unfortunately, it idles at appr. 1400 rpm and I do not have any brake assistance. Maybe I forgot to connect a hose so that I do not have sufficient vacuum?

1)
I need an OBD-reader. My garage doesn't have a proper computer for this model. Which affordable OBD reader do you recommend for this model?

2)
Which sensors might be malfunctioning? How can I test whether it is a defective MAF-sensor or something else?

 

[exp500]

Kowalski- BAFX has a decent bluetooth, It will do alot but not any 2 way EG-Commanded such as ABS or heater. transmission/ Tcase/ 4x4/ . The VXDIAG clones are good, you may need to find a retailer in your country, Here are a couple examples-
https://www.chinacardiags.com/whole...or-gm-saab-opel-suzuki-isuzu-holden-1011.html
https://www.chinacardiags.com/whole...-gds2-diagnostic-tool-wifi-version-17410.html
https://bafxpro.com/products/obdreader

As far as how its running- Follow your Brake booster hose back to the intake, you will probably find a leak there. Recommend to test for vacuum leaks with Brake Kleen or similar, small dribbles along suspect area. If it is leaking rpm will change.
Likely that you still have a check engine light on. See above posts.
Keep Updating us!

 

[YukonGTmaster]

I used a wrong mark on my pulley - you were all right. So yesterday, I found the correct mark and was able to install my new distributor correctly.

But still, it is idling rough with strong smell of unburnt gas. I then disconnected the mass airflow sensor and it then ran smooth! Unfortunately, it idles at appr. 1400 rpm and I do not have any brake assistance. Maybe I forgot to connect a hose so that I do not have sufficient vacuum?

1)
I need an OBD-reader. My garage doesn't have a proper computer for this model. Which affordable OBD reader do you recommend for this model?

2)
Which sensors might be malfunctioning? How can I test whether it is a defective MAF-sensor or something else?

I went with OBDLINK MX+ bluetooth scanner. I downloaded DashCommand off the App Store, and did the in App GM Extended Parameters for $9.99, which allowed me to read Cam Retard Offset to dial in the distributor.

 

[Kowalski]

Dear all,

thank you very much for your valuable information! With your help I was able to fix the problem:

It costs 12 USD (10 €): A spray can of mass airflow sensor cleaner and 10 minutes!!! It was that simple! Engine ran smooth of cleaning the MAF sensor.

Unfortunately, I did the cheap fix after installing a new MFI injection spider and a whole new distributor, wires and spark plugs. Ok, It was not a waste of money because the distributor was old was the old plastic style model and from I have heard it was also not too bad to convert to the new style MFI injection. So all in all not a waste of money.

I did also a bad mistake when I reassembled the upper intake - I forgot to connect the main vaccuum hose to the upper manifold. Now it idles at 600 rpm including brake assistance again. Thanks for your hint, exp500.

I also ordered a bafx-OBDII reader and will then use the DashCommadn-app like YukonGTmaster recommends or the Torque Pro-app in order to set the right timing of my new distributor (idling could still be a little smoother I guess).
Secondly, I ordered a new MAF sensor but not the original Delphi but a Walker model. I know, maybe I should have invested these 60 $ more to get an OEM part, but after spending 1000 USD for parts which were not essential to get it running I was a litlle greedy.

I am really happy now! Next week I need to get a new "Warrant of Fitness" and I hope that the inspector will not find any other defects.


So again, thanks to all of you!


Best whishes
Falco

 

[exp500]

Kowalski- Glad you were successful! Good Job, many suffer long hours with similar. What a Test of your abilities. Welcome to the boards And continue posting.