Another '89 bucking like crazy...

[Frisbeeguy]

This used to be a intermittent problem. At first just wriggled the wires leading to the Cam Sensor solved the problem.

Later, replaced the Cam Sensor and it seemed to solve the problem.

It's come back... violent bucking / jackrabbiting which goes away immediately upon engaging the clutch. Very hard to drive or get up to speed at all. It struggled a few miles but made it home.

Replaced the Cam sensor again yesterday - no change.
Plugged in another DIS - no change

When checking codes I got:

KOEO = 79, 19
KOER = 91, 77

After changing the Cam Sensor and driving around - it started acting up again like crazy after warming up.

No codes - crazy.

When the "episode" kicks in the tach does surge a bit up & down. It seems the radiator fan kicks on and smooths out the idle some but only momentarily.

Ackkkkk.

About 10,000 miles ago replaced Crank sensor, H2O pump, O2 sensors, new catted Y pipe, New plugs & wires (original equip - NOS)

 

[ViPER1313]

Check the wiring harness behind the intake manifold (at the very rear of the engine bay) that runs from the cam position sensor along the firewall (2 or 3 large wiring bundles wrapped in a mesh like material.) Ensure that they are in good condition. There is a metal ridge on the firewall that they like to rub against. I had a car that did the exact same thing - one of the wires was frayed and was intermittently touching this ridge.

Also ensure that the connector for the cam position sensor is fully inserted, that the pins and connector are in good condition (no corrosion) and that the connectors for that wiring harness at the rear of the engine bay are also in good condition (fully inserted together, no corrosion or melted pins.)

 

[Frisbeeguy]

Going back out to have a look. It was running so good, too!

 

[frosho]

Make sure the ground path for your DIS is good. After swapping my p/s pump at VIR, the car didn't want to run right, and it was giving me cam and crank sensor codes. It turned out to be a bolt on the crossover tube bracket that I had only hand tightened.

 

[FREAK_SHO]

Check the connectors in the cam sensor plug. I had one push out, and would not make full contact with the ends in the cam sensor. Wiggle wire and it would run fine for a bit. Fixed the plug and no more problems.

 

[tommyturbo]

on my 89 a similar problem and codes and for me it turned out to be a bad computer and a dirty mass air. I would continually get codes 19-91 and sometimes a 41? It wasn't until the computer started giving out weird 3-4 digit codes (should be 2 digit) on the scanner that I was able to figure it out. For me it would set the codes almost instantly, but it also seemed to be sensitive to rpm changes like shifting gears.

 

[Frisbeeguy]

Hey, Thanks guys!
I pulled & re-installed the Cam Sensor. It all looks O.K.(?)
Did not see any "problem" wiring while crawling around looking for potential shorts.
No recent work on the intake or change in any of the grounds - everything feels tight.

Went for a (scary) drive. It was O.K. for 5 minutes then sorta like attempting to break a wild horse...bucked like crazy. Need to keep revs very high +3000 to go anywhere. (turning on A/C to start fan did not help)

New codes this time:
11 = all O.K.
19 = CID Circuit failed
63 = TP circuit below minimum voltage. Suspect open TP sensor, harness.
66 = MAF sensor input is less than minimum voltage.

I'm going to take a quick video to post what it's doing and try to post later tonight.

Back at it for a bit then must do the family dinner thing.

 

[luigisho]

Unplug the MAF and see if the bucking stops. If the car runs better with the MAF unplugged then it's.. you know.. bad. The car will not have all the pep it's supposed to but it will run. You can try cleaning it but that is not a guarantee that in doing so, and still getting the same symptoms, rules out MAF malfunction.

 

[St Louis SHO]

PCM, needs moar new one.

 

[Frisbeeguy]

Unplug the MAF and see if the bucking stops. If the car runs better with the MAF unplugged then it's.. you know.. bad. The car will not have all the pep it's supposed to but it will run. You can try cleaning it but that is not a guarantee that in doing so, and still getting the same symptoms, rules out MAF malfunction.

No change when MAF unplugged.

 

[Frisbeeguy]

PCM, needs moar new one.

I tried another DIS... or do I need the PCM that's mounted above the radiator?

 

[Frisbeeguy]

video of car acting up...

Ackkk - don't know how to do anything - work the camera, or post the thing.

Please try here:

http://youtu.be/XhwthGtAMZk

 

[Frisbeeguy]

After video ended it immediately "went bad" again.
As soon as I release the clutch it bucks violently.

 

[frosho]

The PCM is the computer, located behind the glovebox. The part above the radiator is called the CCRM, which is just a box full of relays.

 

[Frisbeeguy]

Ordered a replacement PCM today from ShoSource... hope that solves the problem.
Will post again when replaced & tested.
Thanks for y'alls help!

 

[Frisbeeguy]

O.K. I'm back... just got a new (used) PCM in from ShoSource.
Plugged it in and no change.
Car starts and is "pulsing" at idle.
New codes (now 3 digit w/ the gen 2 PCM)
564
214

I'm thinking I need to start unwrapping the wiring bundles starting w/ the wiring leading to the cam sensor and looking for a fault.
Does this sound like the best way to locate the problem?

Thanks

 

[Frisbeeguy]

Check the wiring harness behind the intake manifold (at the very rear of the engine bay) that runs from the cam position sensor along the firewall (2 or 3 large wiring bundles wrapped in a mesh like material.) Ensure that they are in good condition. There is a metal ridge on the firewall that they like to rub against. I had a car that did the exact same thing - one of the wires was frayed and was intermittently touching this ridge.

Also ensure that the connector for the cam position sensor is fully inserted, that the pins and connector are in good condition (no corrosion) and that the connectors for that wiring harness at the rear of the engine bay are also in good condition (fully inserted together, no corrosion or melted pins.)

This is great advise for finding the problem... I didn't see any problem w/ the wiring bundles. They all are tight and sound - no fraying or wear that I can see.
I also just replaced the Cam sensor and the connector looked fine.
This is a southern car w/ 75,000 miles... no rust.

It is no longer an intermittent problem... It's messed up!

 

[93rev2sev]

If the idle is surging, there's a vacuum leak. Check your intake couplers, specifically the end tank.

Also, simply unplugging the MAF sensor will make the computer default to a known good fuel map. If you run the car with MAF unplugged and the jerking goes away, then it's your MAF sensor. This is the easiest test there is for jerking and surging.

 

[Off Road SHO]

My friends 95 had the exact same symptoms and we cured it by replacing the cam sensor with another used one from my supply. His looked perfectly fine with no oil in the housing, no chips missing from the pickup blades, no bent shutter wheel; everything looked great. Put in another used sensor that actually was filthy from its prior life and the car runs like a Yamaha again.

With that all being said, let me just throw something out there. The Crank and Cam sensor wiring is shielded and grounded, through an aluminum foil wrap and a bare bleed wire, back to engine ground. They do this because the sensors are very sensitive and the sensor's signal can be "added to" by one of many different electrical happenings un the hood; the aternator spinning away, the spark plugs firing, the starter cranking. Each one of those create a magnetic field that is in turn absorbed by anything metallic that is nearby.

If the hood or fenders absorb it, no problem, they are grounded and the charge gets back to ground. If wires absorb it, they will transport it to ground as best they can. If a shield around the wires absorbs it and there is a bleed wire attached to the shield, and that bleed wire is grounded at one end, the charge will not reach the wires on the inside. If the bleed wire is no longer attached to ground, the charge will build up in the shield and then induce a charge into the wires within the shield. Which might affect the sensor signal being transported in the wires.

Just a thought.

Tom

 

[Frisbeeguy]

O.K. - thanks for the quick answers... It looks like I can't touch it until Sunday as I'm booked up until then. I'll work on both these and see what happens - I don't think it's the cam sensor itself as the "old" one has only about 6,000 miles on it and the new one is brand new w/ 10 - 15 miles.
I don't relish the thought of unwrapping and tracing the wiring.

Thanks guys for all the tips and help! (got to keep the SHO alive & kicking for another 100,000 miles at least... it'll really drive the wife crazy!)