90 caprice backfire @ 65+

My 1990 Caprice is chuggin at 65 mph or so.
Car was running very poorly. Just about every thing has been replaced. sensors, tune up, fuel pump. Could not figure it out so I took it in, and the third mechanic and $596 later I had new injectors. Now At about 65 or so it will chugg or backfire through the TBI and will stop if I down shift into Drive, but a good amount of acceleration will result in more "chugging". . Took it in for one thing and now this chugging started. 194,000 mi~ good compression.
@ the end of my rope...

My 1990 Caprice is chuggin at 65 mph or so.
Car was running very poorly. Just about every thing has been replaced. sensors, tune up, fuel pump. Could not figure it out so I took it in, and the third mechanic and $596 later I had new injectors. Now At about 65 or so it will chugg or backfire through the TBI and will stop if I down shift into Drive, but a good amount of acceleration will result in more "chugging". . Took it in for one thing and now this chugging started. 194,000 mi~ good compression.
@ the end of my rope...

Can you elaborate on what "just about everything" includes? Was the EGR solenoid replaced? Was the distributor rebuilt or replaced? Was the pickup coil replaced? Was the reluctor inspected?

Also, since we don't have benefit of having been present during the diagnosis, any parameters you can include might be helpful, such as vacuum, actual fuel pressure, base timing, MAP siganl under load, etcetera. Having those kinds of data may make a difference in homing in on the problem.

Ok lets see. Parts that were replaced.... MAP, TPS, EGR, Pick up coil... not sure, been working on this problem for a few years on and off. At first it would only act up when it was warm out. Before he put in the fuel injectors he thought forsure it was the distributor, but it was not, so it was removed. Although they may not have test drove it at speed after install. The reluctor... thats a new one on me. I guess I did not repace everything. what ever I did not replace I tried to check the best I could... knock sensor and the tps circuit. Some of the other stuff that you mentioned is harder for me to check. I can ask the mechanic though.

I replace Fuel Pump and filter, Intake Manifold gasket because it acted like a vaccum leak, loss of breaks at low rpm. I have a Allied Signal Fuel Injection/ Electronic Ignition Manual and tried the best I could, but it was still a little tuff. Oh! The trans has stopped kicking down since repairs have been done.

Unfortunatly I took it back in yesterday and they said that it was the EGR that I replaced... said it was broke and not even mountable...$135. This is the second time that a mechanic has told me not to use cheeper autoparts, he used an OEM EGR. Have you herd this...

Thanx.
I will let you know if that was the problem. Your help is greatly appreaciated. I just realized that I typed 91 instead of 90 as the thread title...!

Well, just picked up car. Did not act up on freeway. But it took about 15 miles before it did last time. Will go for a longer ride later. Other than that it runs a little worse that the last time it was in. It acts as if it has a poorly running Qjet. It even sounds like it, much louder than normal. and when it finally kicks down it like it goes down 2 gears. rpms shoot up and theres a whole lot of noise and not much acceleration.

Its almost like bad timing, im goint to check that now. Maybe trans acting up.

What seems to be happening with your transmission is when shifted into 4th gear the torque converter automatically locks up, and doesn't let go until the tranny drops down to third. My transmission did the same thing, so did the 700 R4 in my van after it hit about 135k. Its not normal, Im not sure what goes wrong in particular, but I do know that it's common.

If the transmission has stopped "kicking down" since the last repair, check/adjust the TV cable at the throttle linkage. Continued operation with a misadjusted TV can cause transmission damage.

Ok, I looked at the kickdown cable and I could not see how to adjust, does'nt look like the old ones. I can keep it in 1st and it still bogs out. My Check engine light went on again...
23 MAP sensor ~ which I have replaced 3 times...
45 Rich Exaust ~
54 Fuel pump Circuit ~

At light throtle it runs good.
At moderate throtle It bogs out and eventually speeds up.
At full throttle Bogs then excelerates and then will kick down.

And I did find the old Pick up coil so that was replaced.

Are MAP sensors testable...? and can they be bypassed, probably not computer needs signal...ugh...

See, my caprice did the same thing as in the three steps you described. The difference is that I don't have any computer, and a carburetor. It turned out to be a vacuum leak from a rotted hose going to the brake booster. Replaced the hose, and the car ran like a top again.

The ECM is reporting a 23? That is not for a MAP signal problem, but an IAT/MAT signal problem. Is the MAT conected?

Your rite, I did have the MAT disconnected while I was running it the other day. Ill have to reset the computer.

Ever since day one it has seemed like a vaccum leak, not as much since the new injectors have been put in. Ill have to go over the hoses again.

The last thing the mechanic said before he sent me on my way was that the only other thing that he could think of was a blocked exaust. I cant afford to take it back to him. Im going to try that too. Disconnect it after the Cat, and take it for a loud ride.

Its pretty cold up here in Michigan about a high of 24 tommorow, but I gotta do what I gotta do.

Hey,
I disconnected the exaust and took it for that loud test drive, it only ran worse. Only code 54 is comming up now~ fuel pump circuit???? I also rechecked the timing. I checked the vaccum, it was reading higher than the normal range on my Vaccum gauge, Norm~15 to 21. I was reading about 23. I am just about otta ideas and money.

Have you tried to unplug the torque converter lockup plug at the transmission and take it for a ride? I know those can do weird things to performance, it would be something easy to rule out and will cost nothing. The plug is towards the front of the transmission, on the driver side.

Bob

yeah its been unplunged for about a year now. When its pluged in its like the trans does not want to down shift when comming to a stop. And yeah there is reduction in performance. I wonder if the trans could be causing the problem, the mechanic said it should not be... but hes been wrong before.

With code 54 Fuel circuit comming up... could this be causing the bogging in the mid rpm range. Lack of fuel pressure???

First, I'll assume (and hope, for your sake) that you have the 4L60/700-R4 transmission, since most B-cars except those with the 307 Olds anchor, err, engine, should have that transmission.

That being the case, if you've been driving around with the TCC unplugged foir some time, the transmission has probably been operating hotter than it should. That can break down the oil faster, and lead to contamination sooner.

As stated before, the 4L60/TH700-R4 does not use a "kickdown cable." Instead, it uses a Throttle Valve cable which replaces both the kickdown cable and pressure modulator found on earlier TH350s and TH200-4Rs. The TV cable acts directly on the pressure regulator for the pump output. It is imperative that the cable is adjusted properly to allow correct shift points and to prevent unnecessarily high operating pressures.

The common reasons that a TCC sticks in these transmissions is either a sticky actuator in the torque converter (less likely), a problem with the wire harness for the TCC or grounding of an ECM input, or a sticking/clogging TCC solenoid valve (more likely). The fact that the trans likely has older, broken down oil could account for either the TCC actuator or solenoid valve sticking, or clogging of the TCC solenoid valve exhaust port. It is possibly that simply changing the oil and filter could clean up deposits and re-establish proper lubrication to the point of restoering correct operation. It is also possible (and relatively easy) to replace the TCC solenoid valve by only removing the oil pan, and with the trans still in the vehicle. A new TCC solenoid valve is under $20. The cost of the valve could easily be recovered in a couple months in the fuel savings alone, not to mention the reduced wear on the engine and trans.

TCC Solenoid (http://www.bulkpart.com/Merchant2/merchant.mvc?Screen=PROD&Store_Code=2&Product_Code=54425B&Category_Code=4L60-700R4solenoid&Product_Count=0)

Checking the TCC wiring is easy enough, and checking the ECM inputs and outputs is also relatively easy.

Either way, changing the trans oil and filter would be advisable, since what you have now may be betyond its service life and already overheated. Once the pan is off it would be very tempting to replace the TCC valve just because, then reconnect the system and see how it works. Of course, installing a drain plug in the trans oil pan would be a good idea to make future changes cleaner and easier.

You also need to adjust the TV cable properly. The TV cable anchor on the throttle body end is mounted via a ratcheting slide. Remove the air cleaner assembly and set it aside. Depress the semicircular detent on the anchored end of the cable housing, then pull the cable housing outward and away from the anchor. This should effectively shorten (take up slack) in the TV cable. With the engine off, open the throttle fully. As you operate the throttle to the wide open position, the cable should pull tight and ratchet the slider in the housing. Once the throttle is fully opened, and the slider has positioned itself, the adjustment is finished. It's that easy. You may want to experiment after a test drive and try clicking the cable ONE STOP ONLY in either direction to establish the desired shift points. Obviously, in order to click it longer you would have to release the ratchet detent again and allow rthe cable to extend one position. A tighter cable should provide higher shift points, and a looser cable should provide lower shift points.

As for the "54" error code you are reading, that could also be due to ECM connection problems, or fuel pump circuit problems, including the ECM/Pump supply fuse and fusible link, shorting of the auxiliary oil pressure switch in the fuel pump circuit, or wiring to the pump itself. You're the only one who can check that, since my meter probes are not long enough to reach there.

I wish I did... I have the 305 with a 200 R4. I would imagine that its the same adjusting sequence. I will try the adjustment first now that I understand how its done, thanx. I have suspected the TCC but wanted to rule out any other possibilities before going in. It would make sence, the overheating, Because this problem has been getting worse over the last 4 or 5 years. At first it would only happen in the hot months, fall, winter and spring it would run great. Thats when about a year ago I unplugged it and it was ok for a while. These other problems came along and compounded the problem.

Hopfully, the fact that I have not been driving it much because of this problem and a trans cooler, I have not done too much damage to the trans.
Ill be getting my DVM out as soon as it gets above 20 degrees...

The TCC solenoid is the same for either transmission. The symptoms are the same. Further, the TH200-4R uses a TV cable like the 700-R4, and the adjustment procedure is the same.

The overheating could merely be a symptom of the clutch not engaging, not necessarily from the clutch slipping. If the TCC solenoid had failed, it would not apply the clutch. That would cause the heating from constant torque converter slippage. However, as long as the TCC solenoid was not applying the clutch, there should be no additional damage to the clutch from driving it that way. You might get lucky and find that clean fluid and a filter, and finding the reason for the clutch not engaging would solve the problem.

20º? Farenheit? It's supposed to be back up to that or higher around here in about a two weeks. Good luck.

Well here's the latest...

The tag on the cowl say's to set timing at 0*
When I got the car a it was set at 12*
And thats how I drove it for 100000 miles.
I tried adjusting it for better performace; no change so it was left at 12*
When I got it back from the shop last week it was set at 8*
It was running bad, no power, poor shifting
I tried setting it at 0* same thing
I went out there yesterday and adjusted the TV cable one notch looser
I started giving the throttle full snaps and it would back fire through the TBI
I thought what could it be but timing since I just had Injectors installed
The chain had been checked by me and the mechanic
So I put a timing light and a vaccum gage on it
I read once: adjust timing for most vaccum and then back off a little
I reved it up... it sounded great
Checked timing It was off the scale
If I had to guess it would be about 25* or so????
I took it out last night It ran great and down shifted good. The jury is still out so ill give it a couple more days before Im sure all's well

Hopefully when it get warm this summer I dont have any problems. All I have to do is work on the TCC issue and the fuel system short (code 54) and I should be good to go. I may wait for spring on the TCC. Without all of you help'n me It may have takin me alot longer.

I just hope this info can help someone elce, save them some of the head aches that I have been through.

Another thought:
The mail man comes by every day while im working on the car, we talk for few about my troublesome car. Well today I told him about how I had set the timing so far in advance... he says "I wonder if the distributor is not set in rite..." I had not even thought of that. It had been removed recently... That kinda makes sence...??? It runs good but there still room for improvement.