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Discussion Starter #1
I have been on this site for a while and I know there are some really knowledgeable guys here. I am having an issue with 97 Bird 4.6 with 201,xxx miles. DTC codes P0172 and P0175 occurred just after 200K and I have been chasing this problem for quite a while. So far I have checked for vacuum leaks and corrected a few minor ones. A friends scanner indicated fuel trims over -15 to 25 range when the engine was hot and noted the hotter the engine got the worse the furl trims got. The cooling fan seemed slow to come on so I replaced the ECT and IAT sensors. I swapped the purge solenoid and still no improvement. I then had a "professional" scan which indicated the MAF was "slightly" out of spec so I replaced the MAF. Fuel pressure was found to be within range. The professional exhausted his list of items to check and ended up with fuel injectors as the problem and suggested using a cleaner to possibly free a stuck injector. Done with no improvement. Lastly, I just swapped out the CCRM from my other 97 Bird to see if the temp issue could be the cause. After 3-4 restarts the CEL was back and so was the P0172 code. No doubt if I drive some more the P0175 will return.

I have read many posts on this site and others and I believe I have checked or replaced all the suggested causes, except for replacing the O2 sensors (which do not seem to be the problem according to the websites) and replacing the injectors.The car runs good with no performance issues although gas mileage does seem to be less than normal. I am not a novice mechanic but not an expert either, especially with all the computer controls on these models.

Any suggestions would be appreciated. Sorry for the long post but I thought more info the better.
 

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Replace the o2 sensors, and check the intake manifold for a leak.

A leak at the exhaust manifold will also show lean.
 

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Discussion Starter #4
Thanks for the replies(2). I am somewhat surprised by the comments regarding the O2 sensors as most of what I have read indicate the O2 sensors are usually not the cause, only the device that signals the problem. What are your opinions about the engine temp affecting the fuel trims as indicated by one of the scans? And how would the O2 sensors affect ECT?

And the comments about the leaking manifold causing a "lean" condition does not seem applicable as there is a "rich" condition on both banks.

I just don't want to change parts trying to find the problem.
 

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Discussion Starter #6
So if I should have replaced the O2 sensors at 60K does that mean I need to change them 3 times? (hehe) The curious thing is there had not been any issue in engine performance and no CEL until after 200K. Regular maintenance- oil, filters, lubes, etc but no other issues engine wise. It's like a switch went on at 200K but performance is still OK.

Where would you suggest I use a vacuum gauge upstream from the cylinder heads?
 

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Brake booster line is a good place to grab vacuum from IMO.
 

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Discussion Starter #8 (Edited)
OK - sorry it has taken so long to reply. I've been busy with other issues. I replaced both O2 sensors(pre-cat) with NZT (OE style) with no improvement. P0172 and P0175 are back almost immediately. Back to engine temp possibly being an issue. As reported b4 I replaced the ECT sensors. I note the cooling fan does not seem to come on for an extended period of time. Gauge temp shows at approximately 1/3 of operating range. Infrared temp shows temp at outlet at 190 F which seems to be in line with 195 F t-stat. Fuel trims are normal until engine temp rises. Turn on the AC which starts the fans regardless of engine temp and fuel trims drop to normal immediately. Scan shows MAF at 0.2 lbs/s. Next I am going to replace t-stat (current one is about 8 years old) and flush cooling system.

As stated b4 there is no performance issue. NO rough idle, No stumble on accel, No lag.

Any other suggestions are welcome.

Oops - my bad. I reported the MAF value as 0.2 lbs/s when it actually 0.02 lbs/s. I presume that means pounds per second so that would equal 1.2 pounds per minute. Is that what the value should be?
 

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OK. At this point, I'd grab an OBDII scanner and datalog what the ECU thinks is going on.

Suggestion: If you have an Android device with Bluetooth, pick up an ELM327 type adapter, and a copy of Torque (Free or Pro; last time I bought, Pro was $5 or so) and datalog so you have visibility into what the ECU thinks is happening.

RwP
 

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When you checked the fuel pressure, did you test the pressure regulator? A leaking regulator can cause a rich condition. That and a stuck injector would have been high on my list. How did you clean the injectors? Last time I tackled that issue, I had to actually remove them and clean them thoroughly to get them back up to par.
 

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Have you used a test light to verify the injectors on that bank are pulsing like they should and not being hung open? I seem to recall that being more common on 94-5 cars.
 

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Discussion Starter #12
I am not sure how to I check the injectors with a test light. Would that be using a standard 12v test probe connected to the electrical terminal to check for on/off? Is there a procedure I can refer to?

I have a scanner and have checked the "live data" several times. The short term fuel trims range from -3 to +3 fluctuating back and forth with most being close to 0. As the engine gets hot the fuel trims get higher which at least one "professional" thinks is causing the rich condition.I just changed the t-stat and are currently flushing the cooling system. Long term fuel trims are also high, in the 20's but I have not driven the car much so those may not have adjusted.

O2 sensors seems to be working (2 new ones) but one of the post cat sensors is slow to record any value. MAF value is 0.02 lbs / sec. I can't find any reference if that is good or not. I installed a new MAF early in this process which did not correct the situation.
 

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Discussion Starter #14
Wow - a Noid light. Never heard of such a thing. But I am getting A Noid. (lol).

I am not experiencing a rough idle and I have no acceleration issues or any other performance issues. The car accelerates and runs the highway at speed with no problems. That would seem to tell me the injectors are not the problem, but...

One mechanic said the injectors might not be closing completely and therefore causing a rich condition, hence the rec to use injector cleaner. From the tutorial it does not seem the Noid test would show that. (I would like to add that I don't use cheap no name gas, usually Sunoco or Gulf, and I get mid grade fill up every month.

I just made a hour run on I-95 mostly steady at 65 mph and the short term fuel trims were in the range between -4 and +4 with occasional peaks to 6 or 7 +/-. At least when I could look at the scanner. Long term fuel trims dropped to +/- 12 -15 from 24 and 25 readings. Early in the run the fuel trims would spike upon deceleration (coasting) at low speed roads leading to interstate and decrease back to +/- 3 with steady speed or acceleration. ECT was reading 204-206 at 65 mph with AC on. I checked for codes after the run and there were no stored codes however there were 6 pending, 3 each of rich bank 1 and rich bank 2, which has been the case all along. I recorded the data but can't find my connector cord to download the scanned info.

In case you are suggesting I did not clean the MAF, it should be noted the MAF was replaced with a new one with the "matched" housing, not just the hot wire sensor.

A continuing saga. Hopefully this will be resolved soon and someone else can benefit from the info.
 

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Discussion Starter #15
It seems that I found the problem causing the 0172 and 0175 codes - a bad PCV valve. Although it was replaced early in this process, apparently the aftermarket one was not adequate. I have run the car numerous times since changing to Motorcraft with no codes. Fuel trims appear to be normal.

HOWEVER I decided to flush the cooling system and change the t-stat to address the possible heat issue and found the vent tube from the radiator to the Degas bottle(the small diameter line) was cracked and actually broke off during the process.

Next question- other than tbird, Cougar and Mark VIII are there any other rad's that will fit? I have read about the 03 Cobra but I don't think I need to go that radical. The local yard is having a sale on the 4th so I might be able to pick one up cheap.
 

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It seems that I found the problem causing the 0172 and 0175 codes - a bad PCV valve. Although it was replaced early in this process, apparently the aftermarket one was not adequate. I have run the car numerous times since changing to Motorcraft with no codes. Fuel trims appear to be normal.

HOWEVER I decided to flush the cooling system and change the t-stat to address the possible heat issue and found the vent tube from the radiator to the Degas bottle(the small diameter line) was cracked and actually broke off during the process.

Next question- other than tbird, Cougar and Mark VIII are there any other rad's that will fit? I have read about the 03 Cobra but I don't think I need to go that radical. The local yard is having a sale on the 4th so I might be able to pick one up cheap.
TIL I learned that some people call the coolant overflow tank a degas bottle. Thanks for htat.

I've always thought of radiators like I thought of condoms and HDDs -- some items are better of being bought new.
Unless you've found an all copper/brass unit that merits a rebuild, you are better off buying a new aluminum+plastic tank radiator instead of pickup up another used one from the JY of questionable repute. I had one that seemed perfectly adequate (didn't leak) but crud on the inside made it so that while it would sufficiently cool a V6, it couldn't deal with the cooling demands of a V8.

You can physically fit a much bigger Griffin universal all aluminum radiator under the hood but you'll need to fabricate custom brackets and in the case of an automatic, you'll also need to add a separate transmission cooler. It's cheap enough (certainly cheaper than a new Cobra rad).
https://www.summitracing.com/parts/gri-1-26242-x
 

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Discussion Starter #17
Thanks - I checked Griffin but found another source- Radiator Express that has an all aluminum radiator made to fir 94-97 T bird that has trans cooler built in. Their cost is $219.

Not to sound maudlin but with recent medical bills and associated costs I need to be budget conscious. If I can find a decent "used" one for $25.00 I will need to try that. If not I may just go the extra money for an aluminum on, but the 20 year old original in my 97 would still be just fine if that small hose connection had not broken. Often times you can find junked cars with brand new radiators as a result of someone trying to fix a bad head gasket or cracked head /block with a new rad.
 

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I would powerflush any used radiator. Also, be sure to use the factory squeeze-on clamps. I saw an interesting bit on an auto repair show where he claimed the worm clamps put on a lot of pressure in one spot, which is not good for plastic waternecks.

Al
 

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If you don't lube the clamp so that it slides on the rubber easily, all clamps will do this.

Usually there's coolant all over everything, but not always; just be aware. :)

You can have two tight spots and gush fluid out two other spots if you do it wrong. :grin2:

FWIW, The stock clamps will eat the fancy aftermarket silicone tubing, you have to use clamps made for such tubing; they have a smooth inner surface.
 

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I would powerflush any used radiator. Also, be sure to use the factory squeeze-on clamps. I saw an interesting bit on an auto repair show where he claimed the worm clamps put on a lot of pressure in one spot, which is not good for plastic waternecks.

Al
Yah.

I over tightened the one on my 1991 Cougar; the upper neck broke right at the clamp, like I had cut it.

(I have a new radiator; but by putting the hose back on and moving the clamp, I was able to keep driving.)

RwP
 
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