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jwhit
08-13-2004, 06:09 PM
somone please help
my car will run and drive perect under 5lbs of boost as soon as i go to wot and boost goes over 5lbs car starts miising and somtimes backfires but if you let off gas it runs ok again as long as i dont go over 5lbs boost every thing is ok
has anyone had this problem?

kano
08-14-2004, 05:56 AM
i think i have similar problem if im thinking of the same thing,
i dont know whats the problem but im assuming tranny oil is low tat y it backfires ( im not an expert.. but thats my point of view)

superchicken94
08-15-2004, 03:55 PM
Change the spark plugs and wires. Don't get the cheap ones. After your done you will know why, allow considerable time for this act.

J57ltr
08-16-2004, 11:40 AM
Change the spark plugs and wires. Don't get the cheap ones. After your done you will know why, allow considerable time for this act.


Yup plugs and wires. It will get worse. When I first bought my car it started at 5psi then got worse until it was missing at -10hg.

Jeff

supercharged95
08-16-2004, 11:43 AM
another thing to consider is....
what octane are you putting in your car? I always run 93 or higher otherwise my car runs noticeably worse. a while back i was on E and desperate for some petrol, I had no other choice but to run 89 in there and the car ran like arse.

J57ltr
08-16-2004, 11:58 AM
Putting other than premium gas will only cause detenation not the bucking mentioned. It is the plugs and wires for sure. If you look at the wires the originals are marked with the year. If that is the case then you need to change them. Use Double plats only, No Bosch.

Jeff

supercharged95
08-16-2004, 02:37 PM
that's a good point... sounds like it's time for some magnecores. come to think of it, my car was doing the bucking thing as well before i put my wires on. Upon changing them I noticed two were cracked and they all were in chitty condition as well.

J57ltr
08-16-2004, 03:10 PM
No real need for "high performance" wires the stockers are very good.

Jeff

jwhit
08-16-2004, 09:03 PM
No real need for "high performance" wires the stockers are very good.

Jeff
sounds like a plan im new to supercharged cars and would have never thought plugs could cause this problem , i pulled 1 plug and it looks ok but the wires are cheap aftermarkets so they will be replaced i gueess i will do plugs also to see if it clears problem ,what do you think of the premium autolite plug wires ??

J57ltr
08-17-2004, 09:52 AM
Personally I was in the same boat as you. This was my first supercharged car and I couldn't for the life of me figure out why it only bucked at 5psi. That is about the time I looked for information here. That was about 5 years ago.

Autolite wires will be fine, Just make sure that the plugs are double plat. or you will be changing them again. It will probably take about 2-4 hours to change the plugs. Most can be accessed from under the car on a set of ramps. the DR side rear plugs an be accessed just behind the HCU for the brakes (the thing that looks like a master cylinder)

Jeff

aviationstation
08-17-2004, 05:18 PM
jwhit,

Your problem sounds very similar to that which a number of other folks have posted about. I would seriously consider your cam position sensor (CPS) to be the "potential" problem. From what I've garnered, these have a tendency to go out more often than they should, and they will not throw a CEL or trouble code all of the time. By comparison, an O2 sensor that is out of range is, well, out of range (voltage wise). If it's too low or too high, the ECM will determine that and throw a code. As for the CPS, it may be intermittent.

I say that because I had a similar problem with my 95 SC under heavy load (75%) up to WOT. Lots-o-pinging & hesitation. Once the CPS was replaced the car ran great, timing didn't change, and the power is instant. I recall hesitation as either fuel or spark (or a combination with ECM controlled cars). If a spark plug wire is bad it would likely miss on that cylinder and not cause hesitation across the power band. A decrease in timing, however, would. That's exactly what the ECM would do if a cam sensor was bad or intermittent. I call it limp-home mode, but Ford likely calls it the were-not-responsible-default-timing setting.

I see so many great posts that revert to the spark plug wire as the at-fault component. This, for me, its a difficult to accept. Wires typically do not fail in unison. If bad, they do not cause a lag or hesitation across the entire powerband (all cylinders); they will on the affected hole. The hesitation, I believe, is a timing change (or retard) and/or fuel delivery problem. I think most of use who have spun wrenches, myself included, on most mechanical objects that make power will agree. I've seen blown, nitrous big-blocks (i.e. highly sensitive mills) pull a good run even after a wire or two has been smoke-ckecked by a backfire through the huffer. Replaceing wires may help, but they are not the panacea for all engine woes. Hell, the Model T had bare copper wires (or flats)... On the plugs I'd have to agree. The DP are good, non-massive electrode units that burn at the right temp for the pocket.

In any case, hope this helps. I'd inspect the wires & plugs, but take a look at the CPS and the MAF.

Just my 1.967 cents

M Randolph
in SoCal somewhere in Kali~fornia

-95 Thunderbird SC/5-Spd
-69 GTO 400/T400
-67 Chevelle SS 396/4-Spd
-66 Nova SS 283/T350
-57 Ford Fairlane 2 Dr H/T 312 SC
-Searching for a 69/70 F/B Mustang

J57ltr
08-17-2004, 05:43 PM
The thing that people donít realize about the plugs is that under normal operating conditions they
will run fine but when you increase cylinder pressure that is when the problem occurs. Fact is if
the plugs are old the wires are going to be the same age. I really really doubt the cam sensor
would be at fault with the description given. When the cam sensor goes out or is intermittent the
car becomes hard to start. It usually takes about 3 tries. and once the engine is running the EEC
knows where the crank and cam are in relation to one and other (by default), so the cam sensor
becomes mute. Granted an intermittent connection could cause a problem but it is very rare that
the symptoms described correlate to a cam sensor.

On the plugs you have to look for signs of erosion around the electrode if itís round itís bad, if
the strap is thinner on one side (tapered) itís time for new ones.

If the wires are dated with the year, the plugs are going to be original. Change them.

aviationstation
08-17-2004, 06:16 PM
J57ltr,

I'd agree that a faulty cam sensor would "usually" cause the car to be hard to start. To clarify, my car started without problems, idled fine, ran great... but at 5~7 lbs of boost would hesitate and backfire. All of this occured with no CEL. When I plugged in the Sunnen the code during the KOEO Running Memery test was 214.

Further, the CPS is never a "moot" point as the ECM algorythm uses input from the CPS at rates of up to 15,000 pulses per second. Operationally most ECM's (GM and Ford) read the CPS and CrnPS on a continious basis, regardless of whether or not the CPS produces a signal for the ECM's current-state computation. If the CPS is not providing updates, the ECM will not receive data to indicate how much timing to advance (for example) in the event of increased vacuum & rpm. The CPS provides a zero benchmark, the ECM adjusts timing according to the ZEROIZED signal from the CPS. The ECM (EEC) has absolutely no way of "knowing" where the cam and crank are in relation to one another OTHER than by a CPS and CrnPS. Some older ECM vehicles used only a CrnPS, but the exact time and delivery of the blow-mix was not as critical an issue as with a huffed engine.

I'd have to disagree that "it is very rare that the symptoms described correlate to a cam sensor." The symptoms described were those that I experienced, and the problem was the CPS. Not that rare when AutoZone, Kragen, and our local Ford dealer need to order the part (FMC parts advises me that they gobble up 3~4 a week). I think you'll find that a CPS is a component that is prone to failure. A number of posts alluded to the symptoms and corrective action(s) that have required plugs, wires, and/or a CPS.

I guess what I'm saying is that it could be MAF, O2, CPS, etc. The wires & plugs theory sounds like the Kragen auto guy that asks what year car you have when you need small block chevy rocker cover gaskets. It's not authoritative enough of an answer to to explain the performance degradation. Although, I have replaced wires & plugs and seen improvement, I have NEVER experienced such performance problems due solely to plugs and wires.

But I digress. I'd encourage all SC owners with problems to replace the plugs and wires. I'd also encourage you to swap the air in your tires, the coolant in the radiator, purchase stock in California's Municipal Bonds, and buy some property at the height of hurricane season in beautiful Punta Gorda, FL. :)

M Randolph
in SoCal somewhere in Kali~fornia

-95 Thunderbird SC/5-Spd
-69 GTO 400/T400
-67 Chevelle SS 396/4-Spd
-66 Nova SS 283/T350
-57 Ford Fairlane 2 Dr H/T 312 SC
-Searching for a 69/70 F/B Mustang

David Neibert
08-17-2004, 06:32 PM
But I digress. I'd encourage all SC owners with problems to replace the plugs and wires. I'd also encourage you to swap the air in your tires, the coolant in the radiator, purchase stock in California's Municipal Bonds, and buy some property at the height of hurricane season in beautiful Punta Gorda, FL

M Randolph,

The fact that your problems were cured by replacing the cam sensor is the exception. 99% of the time if it's bucking and or backfiring under boost, it's the plugs, wires or to a lesser extent the fuel filter.

David

jwhit
08-17-2004, 08:46 PM
ok lots of infromation throwing as soon as i get my car fixed i will repost a let every body know what it was i will probaly change plugs and wires since these are to bad on my wallet if this doesnt fix i will probaly try cam sensor if that doesnt fix it i guess dis moudle next . i ran koeo test and koer test with my scan tool only code i get is pass 11 and code 74 brake switch i think i should have had e brake on so im not worried about code 74 i had this issue with gt mustang when i didnt have e brake on running test .
thanks to all that have posted
jeff whitford

J57ltr
08-18-2004, 12:35 PM
J57ltr,


Further, the CPS is never a "moot" point as the ECM algorythm uses input from the CPS at rates of up to 15,000 pulses per second. Operationally most ECM's (GM and Ford) read the CPS and CrnPS on a continious basis, regardless of whether or not the CPS produces a signal for the ECM's current-state computation. If the CPS is not providing updates, the ECM will not receive data to indicate how much timing to advance (for example) in the event of increased vacuum & rpm. The CPS provides a zero benchmark, the ECM adjusts timing according to the ZEROIZED signal from the CPS. The ECM (EEC) has absolutely no way of "knowing" where the cam and crank are in relation to one another OTHER than by a CPS and CrnPS. Some older ECM vehicles used only a CrnPS, but the exact time and delivery of the blow-mix was not as critical an issue as with a huffed engine.


It does become moot, because the EEC will calculate where the engine is in it's rotation. if you were to disconnect the CPS the engine will run, and run as well as if the sensor was there. The EEC can compensate. Now if you lose the crank sensor that's a different story. So yes he EEC will "know" where the cam is in relation to engine movement by way of the Crank sensor and predetermined programing (default) in the EEC.

Jeff

ThunderDave
08-18-2004, 10:55 PM
Jeff,

I hope you'll have the plugs and wires on it by Saturday so I can hear it run. I hope mine is running too so I can bring it by. If the plugs and wires don't do the trick, we could take the 5.0 out of the turbo coupe, put it in the SC and rebuild the 3.8 for the turbo coupe. :D , Nah, that sounds too much like work. Hope the tune up works. I'll test mine in the morning for codes. Thanks for letting me use your scanner.


David

jwhit
10-25-2004, 09:16 PM
i just got time and money to start back on my car again ,installed new fuel pump and now she screams even cacthes 2nd i very happy that shes running good