I need help on my 1996 Eldorado.

[ToxicDepression]

So lately I've been scared to drive my cadi around because I tried to start it a few weeks ago and it "backfired " next to the intake manifold and caught fire under/around the edge close to where the starter is located, it only happens every now and then though. I figured it was a fuel leak from a cracked hose so I replaced it. This car has a few problems accruing for the past year or so and have been slowly trying to repair it myself. I noticed that the main problem is I have to be careful when I give it gas, if I try to floor it, then I hear a (muffled-air) sound inside the engine and won't respond for about 2 seconds, then revs up without gaining its speed. I have taken off the intake manifold and cleaned/resealed the gaskets just in case it has a leak, I also do hear what sounds like a vacuum leak coming from the left side of the intake manifold (standing in front of the car). Iit also has a VERY ROUGH idle. can anyone please help

[rockfangd]

First off Welcome To Caddyinfo.

First off does it have a steel fuel rail? there was a recall that replaced the plastic rail with the steel.

You are probably hearing the blow out valve on the intake. It is on the passenger side behind the power steering pump area.

I am leaning toward a few things,

FPR (fuel pressure regulator)

Catalytic convertor plugged

Maybe a stuck open injector.

Also is the check engine light on? If it is please pull and post the codes.

Does the engine seem to have a misfire? or multiple misfires

[Cadillac Jim]

We have rockfangd and others with experience with Eldorados like your car. My first reaction is to ask that the owner run the OBD codes (see link in my signature block; you start, with the key on (the engine may be off or idling) by pressing the A/C buttons <Off> and <Pass Warmer> buttons simultaneously for about ten seconds, until all the dash lights come on like you just turned on the key, then release both buttons. You watch the dashboard message center while it displays the OBD troble codes, one at a time.

If you can hear a vacuum leak, it is, as rockfangd says, probably the valve in the intake manifold that pops open if there is a backfire. Usually it springs back into place and seals but not always. If you can see the valve, listen to see if you can hear a leak there; if so, see if you can clean the valve and put it back into place. If not, look for another vacuum leak, like a hose off the throttle body or a crack in the rubber manifold between the throttle body and the intake manifold.

Be grateful that your car is designed to deal with backfires. I knew someone with a Porsche 928 who had this happen and it disintegrated the entire intake system and fuel injection. With Porsche prices for parts and repairs, it totaled his car.

[ToxicDepression]

The fuel rail is plastic, I didn't see any cracks on the gaskets but I recently used the silicone "glue " over the gaskets just in case, I will have the codes soon and will post when I do, if I remember correctly, one of the codes was a knock sensor, o2 sensor, and misfire. I only notice a misfire when I (sometimes) try to start it, when it is running it usually has a rough idle.

[KHE]

The fuel rail is plastic, I didn't see any cracks on the gaskets but I recently used the silicone "glue " over the gaskets just in case, I will have the codes soon and will post when I do, if I remember correctly, one of the codes was a knock sensor, o2 sensor, and misfire. I only notice a misfire when I (sometimes) try to start it, when it is running it usually has a rough idle.

There was a recall on the plastic fuel rail at least 10 years ago. Once you solve the engine issue, I would recommend getting the fuel rail replaced ASAP.

As far as the engine issue, have you checked the fuel pressure?

[ToxicDepression]

Not yet, I did however check the fpr and found that it is bad, so im gonna change that.

[ToxicDepression]

Is it "Normal "for the engine to catch fire around the intake with a bad fpr?

[rockfangd]

It should not but on very rare occasions it can. Thats why I asked about the rail. When the rail gets replaced with the recall I believe the new rail comes with a new regulator

[ToxicDepression]

so I pulled the codes and shows as follows,

no acm codes,

no sdm codes,

no tcs codes,

no rss codes,

no ccp codes,

CODE PZ1558 HISTORY,

CODE PC0603 HISTORY,

CODE PC1520 CURRENT,

CODE IP1552 HISTORY,

CODE IR2255 HISTORY,

CODE IR2064 HISTORY ( flashes 3 times),

NO RFA DATA,

PCM?.

also when I pulled the codes with the key on, then I noticed a "low humming" rattling coming from underneath the driver side back seat, not sure if that is anything to be worried about.

[rockfangd]

that is likely the air ride compressor.

You are missing the pcm portion of the codes which are the first ones to be shown.

[ToxicDepression]

when I checked the obd codes the pcm codes didnt show at first, after everything else was flashed then it showed a "solid" PCM? <-------that is literally what is showed, I was thinking that it wanted me to say "yes" or "no" but didnt do anything unless I pushed the a/c off or info reset then exited the OBD? is there something Im doing wrong?

by the way,, Thanks for all the help everyone, I was seriously considering getting rid of my caddy because I had no Idea what else to do or check for, I couldn't find anyone else online that had the same issue with the same model, this site is really helpful

[rockfangd]

when it enters diag mode the pcm is the first module to display codes. Did you try it again?

worst case, when it comes up pcm? just hit fan up then it will go innto the pcm module, then hit up at pcm codes

[ToxicDepression]

Yes the pcm codes are

PC0603

PC1520,

[Cadillac Jim]

These are what I have on my list:

CURRENT
P1520 Transmission Range Switch Circuit

HISTORY
B1558 BCM EPROM Checksum Error
P0603 Control Module Long Term Memory Reset
B1552 Keep Alive Memory (KAM) Error

The IR codes are probably radio codes; I don't have those handy. All three HISTORY codes that I have are probably reflecting that hte battery has been disconnected recently and don't tell us anything.

The NO RFA DATA message means that the car's network is not talking to the remote function actuator. That is the module that talks to your key fob and to OnStar if you have that.

The transmission range switch is what tells the PCM whether you are in Park, Neutral, Drive, etc.

The key thing to do first is to get the fuel rail replaced ASAP. If it's leaking, you have a safety issue. If the car is backfiring and catching fire, it's far past time to get the fuel rail recall fix.

[ToxicDepression]

alright I recently replaced the fuel rail with the recall, the fpr was not included though, I do know that the fpr is bad and it has a very hard time starting, if it does then it will have a rough idle then stall after a backfire, ( im pretty sure that it is because of the bad fpr from the nylon rail) I pulled the new codes and have it here,

PC0107 HISTORY

PC0140 CURRENT

PC0300 CURRENT

PC1107 HISTORY

PC1381 HISTORY

PC1520 CURRENT

PC1599 HISTORY

PZ2152

[Cadillac Jim]

P0107 Manifold Absolute Pressure (MAP) Sensor Circuit Low Voltage
P0140 Heated Oxygen Sensor (HO2S) Circuit Insufficient Activity Bank 1 Sensor 2 [CURRENT]
P0300 Engine Misfire Detected [CURRENT]
P1107 Manifold Absolute Pressure (MAP) Sensor Circuit Intermittent Low Voltage
P1381 Misfire Detected - No Communication with Brake Control Module
P1520 Transmission Range Switch Circuit [CURRENT]
P1599 Engine Stall or Near Stall Detected
B2152 Seat Rear Vertical Motor Position Out of Range

You need to get a new FPR before you can trust the P0300 or even the P0140. I would put in a new FPR, drive it enough to warm it up and hold it at 45 mph or faster for a few minutes to clear out the engine and exhaust, then clear the codes when you park it. The next day, drive it enough to get it thoroughly warmed up, and run the codes after you park but before you turn off the key and see what comes back.

The P1520 is important now. It means that the PRNDL switch is out of adjustment.

Note that the B2152 is a power seat code; I've seen that one when the lumbar support position is up against the stops.

[barczy01]

Check the condition of your spark plugs,wires and make sure your ignition coil towers are clean.

[ToxicDepression]

So I replaced the FPR and also cleaned out the Throttle Body but when i start it it likes to backfire a bit beforehand, but starts up with no problem shortly after it was running. I have gotten it running and let it idle for a bit, I do notice that it likes to hesitate while accelerating on lower RPM then fine at a higher RPM (2,300 ish and up). I Haven't driven it really to go 45 because it doesn't have insurance. Would I be able to "clean" the engine on idle and higher revs?

[rockfangd]

You never answered if you replaced the fuel rail, Unless I missed something. I know you mentioned it had the plastic fuel rail which was recalled. The FPR is part of the replacement rail.

If it is still backfiring there must be something going on. Please post a pic of the top of the engine.

[ToxicDepression]

Yes the fuel rail was replaced, but the FPR was not included tho,

[rockfangd]

Ok thank you. So it now has the full steel fuel rail. Correct?

If it continues to backfire on cold startup I would be concerned.

I would be looking at the coolant temp that the pcm reads to control fuel flow. Sounds like it is running rich on startup to me

[ToxicDepression]

yes it does have the steel rail on it now with the new FPR, where is the coolant temp located? i was also thinking that it might have a blown head gasket, would that also cause these problems to occur?

[Cadillac Jim]

No, head leakage won't cause backfiring on cold starting or poor throttle response at low RPM.

Incidentally, idle to 2500 RPM is the normal operating region for most normal driving.

The engine coolant temperature sensor is on the rear of the right head (driver's side of the rear head).

Before you disturb the ECT, you should make sure that there is a problem with it. If the temperature gauge reads cold when the car has been sitting overnight, and gradually moves to the straight-up position as the car warms up, the ECT and its wiring are OK.

At this point you should look at leaking fuel injectors. I would start with a can of Techroline in the gas; if anything changes, you can add Techroline after every fill-up until the problem goes away or stops improving.

Don't ignore the CURRENT P1520. If the PRNDL switch is out-of-adjustment, the transmission can behave unpredictably. You can probably fix this with an adjustment. If you need help in getting the procedure to do this, ask and we will give you the FSM procedure.

[ToxicDepression]

Yes can I get that procedure from you guys. Every help is greatly appreciated, and yes Rockfangd, it it still running rich on fuel, but it might still be cleaning its self out, when I checked the old FPR than it was leaking so bad like the fuel was made to go through the vacuum line with no restrictions, so yeah it was bad.

[Cadillac Jim]

The DTC P1520 is treated in the 1997 FSM on pages 6-552 through 6-555. The 1996 and 1997 models are almost identical and the differences won't likely be in this part of the car.

There are four switches in the Transaxle Range (TR) switch, all of which switch ground signals to the PCM. This is becaue the PCM controls the transmission as well as the engine; in your car the transmission control module is integrated into, and is part of, the PCM.

Input A to the PCM, pin 74 on connector C1 to the PCM, is a BLK/WHT wire.

Input B to the PCM, pin 34 on connector C1 to the PCM, is a YEL wire.

Input C to the PCM, pin 33 on connector C1 to the PCM, is a GRY wire.

Input D to the PCM, pin 32 on connector C1 to the PCM, is a WHT wire.

The connections in the switch are given in the table below. Where there is a Y, the switch grounds the wire.

The PCM decodes the pattern in the table and sends the gear selection to the IPC over the car's network for the gear selector display.

DTC P1520 sets when the PCM sees a pattern that is not in the table for 3.3 seconds or longer. This can happen if the gear selection switch is out of adjustment so that it is between gears when the gear selection lever is in a detent. It can also happen with a wiring or connector problem, but you should check for good adjustment first.

If the lights for P, R, N, D, 3, 2 and 1 appear in order as you move the gear selection lever, there shouldn't be a problem, unless the display flickers or otherwise misbehaves when the lever is in a detent. If you never get a good display, look for a wiring problem and then check the adjustment when the wiring problem is fixed.

The fact that the DTC is CURRENT all the time is interesting, because the FSM says that the DTC will go to HISTORY anytime a good code is detected from the TR switch. This means that the PCM sees a bad switch code all the time.

Preliminary checks include:

• "The gear select display will box all gear indications and flash on and off if an invalid or suspect gear position is received by the PCM. This will normally occur if the gear selector is not fully in a gear position. When a valid gear position is attained, the gear select display will immediately display the correct position. If the PRNDL on the IPC is flashing, this may be an indication that the shift cable and/or Transaxle Range Switch is out of adjustment."
• If you see the dash display for P, R, N, D, 3, 2 and 1 in order, but the displays when the lever is in a detent, adjust the switch. The FSM refers you to the procedure for DTC P1810 for adjustment.
• If the dash gear indication flashes for all of the gears, check the connector to the TR Switch and also PCM Connector C1.
• If the dash gear indication flashes for some gears but not others, look at the table for the gear selections that cause flashing. The wire that is a Y on those gears but not any of the others may be bad, or a terminal in one of the connectors for that wire is pushed in or bent.

DTC P1810 is "TFP Valve Position Sw CKT Malfunction" and is treated on pages 7-141 through 7-146. This is for the Automatic Transmission Fluid Pressure Manual Valve Position switch (TFP Val. Position Sw.) which is controlled at the lever on the transmission that is moved by the cable from the shifter. It's inside the transmission. By referring you to this section from P1524, they are telling you to check the cable adjustment. This lever must be in the proper position for each gear when the shifter is in the detent for that gear.

The range selector cable adjustment is on page 7-170. The first thing it says is to adjust this cable ONLY while both the transmission and the selector are in NEUTRAL. Trying to do it in another gear will not get it right. The process is an eleven-step procedure that is error-prone and the cable is easily damaged, and three figures are used to illustrate the process. The cable self-adjusts on installation when both the transmission and selector are in NEUTRAL. Unless there has been accident damage or the engine or transmission has been out of the car, I would not do this first.

There is no procedure that I can find for adjusting the TR switch, but it should be obvious. If you can see the dash display, put the shifter in NEUTRAL and lock the switch in the position mid-way between the points that the display turns off the N on the shifter display on the dash.