DavidSamuels
K-Jet-Free Zone
- Joined
- Nov 12, 2007
- Location
- Palmdale--Hi Desert, N of L.A.
Good morning to the board. I don't usually post such requests, since I do this for a living, but I've got a 91 wagon here that is stumping me and thought I'd solicit some input from the theory gurus. I hope no one is offended by that.
This is a vehicle we prepared for an indie movie a couple of years ago here in L.A. 1991 245 automatic. The group drove it cross country during the filming and it has since become the "mule", hauling all their equipment for other films. It's not very well cared for, sadly. It is here because it failed smog and the regular mech in L.A. quoted them some outrageous price, even for a Cali cat, which granted is expensive.
Seeing the original cat still under the car, the first thing I did was replace that, and in fact the entire rotted exhaust (car is California originally, but lived in the midwest for years). The cat we installed is a known good, aftermarket unit, with very little mileage. We ran it through the sniffer and the NOX dropped from 2400 ppm to 199, so that passed. However HC and CO are till too high. Granted cats aren't always "all good", but read on....
We ran full diagnostics on the car. First thing that showed up was a slow 02 sensor, biased toward the top, so that went. Now we have a fast 02 sensor, that cycles down to the lower part of the scale, about .3 volts, but generally speaking is showing a rich condition. It oscillates between about .42 and .8. Once in awhile it will drop down to .3-.35, and about every twenty cycles we may see a .28, but rarely. In the two days I spent with the car, mostly idling, but with a few trips around town, it used up a bunch of fuel. Call to the owner confirmed mileage has gone to hell recently. Rough estimate, 12 mpg.
Here's what has been done: ECT replaced, old one was out of spec, but there were no starting problems and the car runs very well. New one reads correctly from the ECU, .5 volts at temp, confirming no wiring issues. EGR pulled, cleaned, tested good. Vacuum elbow was holed, replaced that along with several other minor vacuum fixes. Fuel pressure is correct at around 39 and is correct through rev range. TPS checks good. IAC valve is good, and clean. Oil is fresh, no smell of gas. Intake snorkel is new, old one had holes. We have a new AMM installed for testing, though it made no difference, the old one checked good. Injector seals are good. All four injectors are good and not leaking, and yesterday I pulled the cold start injector to make sure it's not dripping (what a pain). Rotor, cap and wires have been changed for stage 1, no difference. Plugs are tan/brown, not overly lean, but not dark. I would expect them to be darker. Car is running a 556 ECU, but changing it out for several others made no difference. We cannot hear or feel any exhaust leaks.
The owner complained of the temp gauge doing funny things. We assumed it was the compensator board and serviced that, but in fact the gauge was not fluctuating, it was simply staying cold. That was an "oh yeah!" moment, and a new thermostat solved the problem, but running cold and causing ECT issues was apparently not THE problem.
I am down to a few things to check. First, I checked idle timing, but haven't checked at higher RPM. I suppose the CPS could be bad. Or even the EZK, though not likely. Too much advance would sure kill me as would too little. Yesterday I found Trichard's post on Brickboard about cracks in the headpipe, inside the heat shield, allowing air to get to the 02 sensor. This car had a screaming rattle until we removed the bellhousing support bolt to the headpipe. I am going to look at the possibility that the headpipe is damaged, but the exhaust is quiet.
The only other thing I notice is that the car seems a little bit down on power. 240k miles, not a youngster, but neither is it old. We did the timing belt, but that was a long time ago and I'll bet the owner never had the tensioner adjusted. Here's where the theory comes in.
I want to check today and see if the timing belt has jumped. The ignition timing is right on, but if the cam timing is retarded, with subsequent late opening, I'm thinking we may be flushing unburned fuel right out the tailpipe. Certainly retarded cam timing takes the performance down. It's not a huge thing. I just "feel" that the only way the car performs is if you really lean into the throttle--more than normal. My question, has anyone had issues with high HC and cam timing?
No dragging brakes, trans is fine, have been over the engine bay five times--no vacuum leaks, checked with the smoker too.
Aside from the cam thing, I'm hoping someone is going to chime in with something I've overlooked. Sometimes you stare at something so long you miss something.
(obligatory TB emoticon issued).
Thanks to all. Again, I don't usually ask for repair help, but this one is killin' me.
Dave
This is a vehicle we prepared for an indie movie a couple of years ago here in L.A. 1991 245 automatic. The group drove it cross country during the filming and it has since become the "mule", hauling all their equipment for other films. It's not very well cared for, sadly. It is here because it failed smog and the regular mech in L.A. quoted them some outrageous price, even for a Cali cat, which granted is expensive.
Seeing the original cat still under the car, the first thing I did was replace that, and in fact the entire rotted exhaust (car is California originally, but lived in the midwest for years). The cat we installed is a known good, aftermarket unit, with very little mileage. We ran it through the sniffer and the NOX dropped from 2400 ppm to 199, so that passed. However HC and CO are till too high. Granted cats aren't always "all good", but read on....
We ran full diagnostics on the car. First thing that showed up was a slow 02 sensor, biased toward the top, so that went. Now we have a fast 02 sensor, that cycles down to the lower part of the scale, about .3 volts, but generally speaking is showing a rich condition. It oscillates between about .42 and .8. Once in awhile it will drop down to .3-.35, and about every twenty cycles we may see a .28, but rarely. In the two days I spent with the car, mostly idling, but with a few trips around town, it used up a bunch of fuel. Call to the owner confirmed mileage has gone to hell recently. Rough estimate, 12 mpg.
Here's what has been done: ECT replaced, old one was out of spec, but there were no starting problems and the car runs very well. New one reads correctly from the ECU, .5 volts at temp, confirming no wiring issues. EGR pulled, cleaned, tested good. Vacuum elbow was holed, replaced that along with several other minor vacuum fixes. Fuel pressure is correct at around 39 and is correct through rev range. TPS checks good. IAC valve is good, and clean. Oil is fresh, no smell of gas. Intake snorkel is new, old one had holes. We have a new AMM installed for testing, though it made no difference, the old one checked good. Injector seals are good. All four injectors are good and not leaking, and yesterday I pulled the cold start injector to make sure it's not dripping (what a pain). Rotor, cap and wires have been changed for stage 1, no difference. Plugs are tan/brown, not overly lean, but not dark. I would expect them to be darker. Car is running a 556 ECU, but changing it out for several others made no difference. We cannot hear or feel any exhaust leaks.
The owner complained of the temp gauge doing funny things. We assumed it was the compensator board and serviced that, but in fact the gauge was not fluctuating, it was simply staying cold. That was an "oh yeah!" moment, and a new thermostat solved the problem, but running cold and causing ECT issues was apparently not THE problem.
I am down to a few things to check. First, I checked idle timing, but haven't checked at higher RPM. I suppose the CPS could be bad. Or even the EZK, though not likely. Too much advance would sure kill me as would too little. Yesterday I found Trichard's post on Brickboard about cracks in the headpipe, inside the heat shield, allowing air to get to the 02 sensor. This car had a screaming rattle until we removed the bellhousing support bolt to the headpipe. I am going to look at the possibility that the headpipe is damaged, but the exhaust is quiet.
The only other thing I notice is that the car seems a little bit down on power. 240k miles, not a youngster, but neither is it old. We did the timing belt, but that was a long time ago and I'll bet the owner never had the tensioner adjusted. Here's where the theory comes in.
I want to check today and see if the timing belt has jumped. The ignition timing is right on, but if the cam timing is retarded, with subsequent late opening, I'm thinking we may be flushing unburned fuel right out the tailpipe. Certainly retarded cam timing takes the performance down. It's not a huge thing. I just "feel" that the only way the car performs is if you really lean into the throttle--more than normal. My question, has anyone had issues with high HC and cam timing?
No dragging brakes, trans is fine, have been over the engine bay five times--no vacuum leaks, checked with the smoker too.
Aside from the cam thing, I'm hoping someone is going to chime in with something I've overlooked. Sometimes you stare at something so long you miss something.
(obligatory TB emoticon issued).Thanks to all. Again, I don't usually ask for repair help, but this one is killin' me.
Dave
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