Runs rough tach inop

[maloneysforever]

I was wondering if anyone could point me in the right direction on this. I just got done doing some work to my 85 Grand National and when done the car runs like it has a miss and the tach is inop. Before I worked on it the tach worked (just replaced the part in the cluster this last summer) and it ran great. Here is a list of the things that I did.

Replaced valve cover gaskets.
replaced the wiring connector for the wastegate solanoid
fixed loose wires at the starter solanoid
replaced the negative battery cable
replaced the 2 dash speakers
installed missing light bulbs in the instrument cluster for the temp/volt lights
replaced light bulb for the heater control panel

I am hoping that someone could point me in the right direction of what I screwed up. I already checked to make sure that the firing order is correct.

 

[maloneysforever]

Well I just figured out the tach problem and it was not related to the running rough. I removed the two instrument cluster bulbs and it started working again. I let it warm up this time and the threw a code 44 o2 sensor lean. At aldo the o2 voltage is around 15-18 but goes lower. I also triple checked the firing order and replaced the spark plugs but there was no differance. I also forgot to add in the begining that I replaced the pcv valve and hose also.

 

[Rottydogg84GN]

I would start by looking at all my rubber hoses. because an air leak will kill your tune and make you want to pull your hair out. get a scanmaster its a must for tunning. And last but least ask questions and read the older fourms on our cars. All this just my 2cents.

 

[Jerryl]

Well I just figured out the tach problem and it was not related to the running rough. I removed the two instrument cluster bulbs and it started working again. I let it warm up this time and the threw a code 44 o2 sensor lean. At aldo the o2 voltage is around 15-18 but goes lower. I also triple checked the firing order and replaced the spark plugs but there was no differance. I also forgot to add in the begining that I replaced the pcv valve and hose also.

I would look into the O2 sensor, verify operation of the temp sensor, and MAF sensor.
My $$ is on the MAF, but it's like playing the lottery without scantool data.
Let us know what you find.

 

[maloneysforever]

I check for vacuum leaks today and found none. I have a scan tool a OTC 4000 and here the the specs.

idle 750
temp 190
02 .14
egr on
iac 24
blm 150
maf 005 g/s
knock ret 00 deg
code 44 o2 lean
cross 02 000
lv8 029
int 150
tps .44

is it possible that the bulb that I put in the instrument cluster and made the tach stop working (only had one bar and would not change) could have back fed into the ignition module/coil and damaged one or the other of them? I really feel pretty lost right now.

 

[Jerryl]

I check for vacuum leaks today and found none. I have a scan tool a OTC 4000 and here the the specs.

idle 750
temp 190
02 .14
egr on
iac 24
blm 150
maf 005 g/s
knock ret 00 deg
code 44 o2 lean
cross 02 000
lv8 029
int 150
tps .44

is it possible that the bulb that I put in the instrument cluster and made the tach stop working (only had one bar and would not change) could have back fed into the ignition module/coil and damaged one or the other of them? I really feel pretty lost right now.

"Cluster light" and "rough running" are mosre than likely two seperate issues.
These are unrelated.
Do a search for "Tach recalibration".

BLM and INT of 150 means the ECM is adding fuel to keep the motor happy, and is maxed out.
Does the car smell rich and what do the plugs look like?
How old is the O2 sensor?
Did you verify battery voltage and fuel pressure?
What fuel is in the tank?

 

[maloneysforever]

Fuel pressure is 38 psi with the regulator vacuum line unpluged
93 octane from BP that is two weeks old(this car is a everyday driver)
battery voltage is 12.5 volts and the altenator is putting out 14.1 while running at idle.
02 was replaced this last spring about 7,000 miles ago.
I just changed the plugs out last night and put new ones in and the ones that came out looked worn but good other than that.

LIke I said it ran perfect before I did that work so I had to of screwed something up. I have retraced all my steps but can not see anything for sure.

 

[Jerryl]

Fuel pressure is 38 psi with the regulator vacuum line unpluged
93 octane from BP that is two weeks old(this car is a everyday driver)
battery voltage is 12.5 volts and the altenator is putting out 14.1 while running at idle.
02 was replaced this last spring about 7,000 miles ago.
I just changed the plugs out last night and put new ones in and the ones that came out looked worn but good other than that.

LIke I said it ran perfect before I did that work so I had to of screwed something up. I have retraced all my steps but can not see anything for sure.

Strange.
Numbers look good, but, BLM still maxed out.
Not sure what the work you did could have done to get this condition.
Can you “undo” the work? :tongue:

Seriously, I was thinking an “exhaust leak” next, but, if plugs look good, than something is wrong.
I am also thinking “chip does not match injectors” (Injectors a lot smaller than chip calls for), but, it ran fine before you made the changes.

Guess, I’ll have think about this for a while, and I am sure someone else will have better insight. :frown:

 

[BRAD_PADGETT]

I have an idea which is easy for you to test. When you replaced the valve cover gaskets the coil module and coil pac were removed. Unplug the connector to the coil module and look for any bent pins or dirt. Clean and reconnect the connector. Good luck- brad

 

[turbonut85]

Would an exhaust leak before the turbo...ie: cracked header/crossover/uppipe...cause the BLM to elevate and the car to run rich?? I'm wondering--not trying to suggest a solution. :redface:

 

[Jerryl]

Would an exhaust leak before the turbo...ie: cracked header/crossover/uppipe...cause the BLM to elevate and the car to run rich?? I'm wondering--not trying to suggest a solution. :redface:

I have an idea which is easy for you to test. When you replaced the valve cover gaskets the coil module and coil pac were removed. Unplug the connector to the coil module and look for any bent pins or dirt. Clean and reconnect the connector. Good luck- brad

All GREAT suggestion fella’s!
An exhaust leak before the O2 most likely will lower the NB O2 reading (Read lean)
But no exhaust work was done, and the car ran fine before the other changes.

Brad,
You bring up and excellent point!
I would think that a misfire would indicate rich condition, but, since the O2 sensor reads oxygen, that is unburned, it would read lean, and max the BLM.
But .............. the plugs look fine, so, I donlt know.

 

[maloneysforever]

I did have to remove the turbo up pipe from the header to turbo and loosen the down pipe from the turbo to access the passanger side valve cover. I checked already for leaks but did not find any but I will double check again tonight.

I did not have to remove the coil/module at all to do any of the work but I will also remove it and check the harness connector for loose/dirty wires tonight when I get home.

Thanks for not giving up on my guys I really appreciate it.

 

[maloneysforever]

I was unable to find any problems with the coil/ignition module wiring and there were no leaks in the exhaust at all.

A friend thinks that there might be a possibility that I knocked a rocker shaft off/loose when trying to fish out the passanger side that is such a tight fit. Is that possible to even happen? There are not any noises coming from the engin at all. I will probally do a compression test tonight when I get home to test that theory.

Also could it be possible that the Mass air flow sensor could cause this problem? I had to disconnect it and remove it to access the drivers side valve cover gasket.

 

[TType84]

shouldnt o2 be showing some crosscounts?

i would swap out the o2 with a new one to be sure. it should be covered under part warranty, no?

 

[maloneysforever]

I am still trying to figure this one out. I am leaning towards the ignition module or MAF. I see that if I replace the ingition module I will need to use a 87 module since the 85 is no longer available. I see that I will need a wiring adaptor and a plate adaptor to go between the module and the bracket but can anyone tell me if my 85 coil will go onto the 87 module.

 

[TType84]

you can make a plate if you're mechanically inclined...

 

[turbonut85]

No.

 

[maloneysforever]

I finally figured it out. It was the ignition module.

Thanks to all that replied.