Hello All,

Just purchased a 1992 Bonne as a second car (need to keep some miles off the benz )...but it has a few problems.
I know the car has been taken care of (i have reciepts for alot of the work done), but it is old - 174k+ mileage. Just before it was taken off the road, over 9 months ago, it had some serious problems. It was scanned and found to have a bad computer, and two bad sensors. Unfortunately, i do not know which sensors. All 3 (computer, 2 sensors) were replaced with new parts. From what i have been told, shortly after there it had the problem of stalling randomly. When you would take your foot quickly off the gas, it wouldent rev high enough to keep it idle. The seller (a trusted friend) sold it to me - with me aware of those problems, and the information that it was one sensor...calling it the SPT sensor. I've never heard of a SPT sensor, but if you play scrabble...it'* errily similar to TPS (heh).

First time we started it in 9 months, it idled ok and ran good. The day i picked it up i filled it with 93, and a STP additive (fuel system cleaner maybe?). Being as it was coming close to dusk, and i needed it the next day, i brought it to Pep Boys to get the oil changed (I've NEVER let a shop change my oil, and use only Castroil and Mobil 1), and picked up a TPS sensor. It has been running good, but i haven't noticed much since i replaced the TPS sensor. It only occasionally stalls...usually while creeping very slowly into a parking space, heh.

EXCEPT Today - it did something different though...while driving on the highway, i had to brake, and slow to about 45. I started to accelerate after, and realized something wasn't right - it was doing around 4K at 60 MPH, and seemed like it didnt want to slip into OD. Nothing would kick it back in, but a couple mins after it all of a shudden shifted into OD and was fine. Shortly thereafter it started idling at around 1,200 - 1,500...then went back to normal.


Sorry about the long post, but i don't know what information is pertinant and not.
My main questions are:

-What sensor could be causing this stall?
-Is there anything else i should do to this car, after it'* been sitting 9 months, to prepare it for a daily drive (40-80m/day)?
-Is it a big difference to use 87 vs 93?
-Why would it not shift into OD?
--could it have something to do with the stall problem?
-Any other general "good" ideas to do with the car?

I know for sure that the suspension has been re-done all around, new brakes/rotors, new U joint left front - i have reciepts for all of those.....
Now this being a second car, i can "take it" for a day/couple days and do some work to it. The car was a steal - at $600. At first it was gonna be a beater, but i've taken a like to it. What, in order of priority and cheap > expensive, should i look into replacing/refurbishing?

Read through the site alot and i hope someone can shed light on a bit of this for me. Again, i appologize for the long post, but i tried to provide as much info as i could. Thanks in advance!

92' L27. Cool. Right off the bat, is the top of the motor black or aluminum.

Umm... Intermittent stalling... *grabs FSM*

Rough, unstable, or incorrect idle, stalling.

Definition: Engine runs unevenly at idle. If severe, the engine or vehicle may shake. Engine idle speed may vary in RPM. Either condition may be severe enough to stall engine.

First things to check: Vacuum Leaks. PCM grounds.

Fuel System: Fuel in the vacuum line for the FPR. Unbalanced Injectors. EVAP problems. O2 Sensor dying.

Ignition: Plugs wires ETC.

Engine mechanical: cylinder compression. (I got 160psi on my car). Incorrect cam or weak valve springs.

Additional checks. EGR system. Throttle linkage for sticking or binding. IAC Operation. A/C malfunction.. PCV Valve malfunction. Broken motor mounts (Front tranny mount most probable). Broken alternator.

I bet everyone can agree, if you check the plugs, wires etc. Look for the name Bosch on anything. If you see it, replace it. Bonnie'* hate the name and act up usually upon reciept of a part with the name on it.

O2 sensor sounds like a good possibility. Do you have any access to a scan tool? If so check the O2 sensor, it should fluctuate high to low. If not, that would be a good start. Also checking those grounds is another big one.

I would start by replacing the o2 sensor, then changing plugs(DON"T USE BOSH)wires if they are look old, then changing the tranny fluid, flush the cooling system and change the t-stat, air filter,and then get something to clean the throttle body and change the fuel filter. These are things I do to any used car I get no matter what the service records. If the tranny fluid is old it can cause problems. Stalling or spurt could be caused by plugs and or o2 senor is dying and or dirt fuel filter and or air filter.That will give major tune up It will give you a good starting point

Thanks for all the suggestions.
Couple things...
the top of the engine is black.
I have access to a Snap On ORBII scanner...i think i'll be checking it sometime this upcoming week. That should narrow it down a bit. I was thinking of picking up new plugs and wires this weekened......anyone have any suggestions? how much should it run me?

Damemorder:
You described my car to a T. The engine is filthy, and i haven't had a chance to hit it with Purple Power....but i'll clean the whole thing then look for vacuum leaks. Hrmmm.....i know for pressure leaks, you use soapy water and look for bubbles....any tips on how to quickly find a vacuum leak?

As far as grounding goes, i don't think thats any major problem...i do electrical, and usually when it is a problem you'll notice dimming lights or other things....but does a 4GA wire from bat > engine, and 4GA wire from bat > chassis sound like a good idea? i'm looking at a 100' spool of 4GA wire...so i think thats something that can't hurt.

What exactly is the PCM, and whereabouts is it located? Throttle linkage is good and doesn't stick. Alternator is good...battery was dead, charged it, started car, and it'* been running strong since. If AC is good and blowing cold.

O2 sensor could be a likely candidate...had one of those go out on the benz (Except it had 2 of them...dealer wanted $300 each, found em for $175 each ) How much should it/they run me?

BillBost37 & Masterbm:
Right on overflow tank, in permenant marker, is: "Coolant system flushed: 30,000 miles, 120,000 miles"...so i can check that off for a little while. How hard is it to change tranny fluid? It seems a cheap thing to do, but a very helpfull one.



Thank'* for all the suggestions guys. If someone could point me to directions for the Tranny Fluid, i'll take some pics along the way and post 'em up for other people. You all seem to know what you'r talking about, and i appreciate you helping me. Thanks again!

calibrate the sensor? hmm...never heard of that....how would i go about doing that? and the SES light is fickle....sometimes it'* on...and sometimes it'* off....and as far as the top of the engine color, i cleaned it up...and where you fill the oil is silver (well silve w/ black striped) so i'm not sure where the difinitive "engine color" is?

I was checking vacuum lines, and it seems there aren't that many? i see one coming from the firewall, to somewhere by the fuel line. Then from there, theres two solid tubes that go down the front of the engine, to two other vacuum lines (one goes to what looks like a large "cup" on the right side, in front of the winshield wiper fluid)
There any other major vacuum lines i should be looking at? I cannot find any wiring damaged, bent, etc. Messing with sensors (moving wiring, tapping it), figurign maybe it was a faulty sensor, i cannot find anything definitive. I'm kinda stumped here....

I plan on replacing wires, plugs, and changing tranny fluid....but the latter would have nothing to do with idle (but since i want to keep that tranny running top-notch, it will soon recieve a overhaul ). o2 sensor, thermostat, and and fuel filter have been suggested....but i've had problems with all of those in the past, on previous vehicles, an this has never been a side effect. Before i go buying a o2 sensor (i assume some decent $$), i wanna find exactly what is wrong.

I'm gonna bring the car in on mon or tues and see what codes i pickup.

I appreciate the help, guys. Since i don't have much experience with bonne'*, and know just enuff about an engine to get myself in trouble, i've been lurking around the electronics forum (my specialty). Thanks again!

UPDATE

Just scanned it with Snap-On diag.....dead TPS sensor
Just replaced it...and it'* DEAD?!?!? PepBoys is gonna get a piece of my mind. Now i gotta get a new one, and tap out that screw, and throw a new one in....argh

Time to check wiring, bud.

Just so you know:

I find vacuum leaks with carb cleaner, If the RPM spikes, You found the leak. If the car lights on fire, You sprayed something hot. Don't do that.

The PCM is up under the passenger side of the dash, silver box, three connections, 10mm nut to remove.

02 sensor is about $60-$70. There'* only one.

If you look at the top of the engine, the plastic cover that says "3800" real big surrounds the "engine color" defining peice. Black is good. Aluminum means you have no EGR.

Vacuum lines:
Engine to Brake booster, biggest line.
Engine to Vacuum canister on firewall, small line. Has a Tee on it going to the cruise control box on top of the trasmission.
Engine to transmission, bigger of the two lines heading that direction, it'* for downshifting.
Engine to EVAP canister, smaller of the two lines going that way, They're the two lines that have a u bend peice on the engine end.

To calibrate the TPS sensor takes a Modifacation. You have to drill out some holes and things. Since you're going to buy a TPS anyway.. I suggest you buy a TPS for an '87 Bonneville. It fits perfectly and has the same values (they're both just 5K linear pots). Put the tps in place and put the screws in just enough to hold the TPS'* position. Hold the throttle wide open (engine off of course) and adjust the TPS until you get over 4.5 but well under 4.8 volts from Pin B to Pin C. The idea of calibrating the sensor is to make sure you can reach "Power Enrichment" mode when you floor it. You never know when you'll need that extra power.

Pin A: 5V power
Pin B: Signal
Pin C: Ground.