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1986 N/A wont rev past 4,000RPM

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Old 03-28-10, 07:06 PM
  #126  
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Originally Posted by Texas_Ace
Well in a strange turn of events, i thought i would update this thread with what fixed my problem.

Then a few hours later i got the new injectors in and swapped the rear secondary out, started it up and all problems are fixed! Runs perfect now!
Congrats! I have been unable to work on my 7 for the past month, so I was excited to see your chain of posts. Looks like you went through everything I was going through (even the key beep). I'm wiating for a weekend that I'm actually at home and can get an extra set of hands to help w/ the injector replacement.

As for your beep, do yourself a favor, replace the tumbler and be done with it. Takes about 30 min, replace the shear-bolts with some pan-allen heads instead of OEM bolts. I paid about $70 for a complete 4 tumbler set w/ key from the used parts fellow in OK. Also, the CPUs can have alot of cold joints. If you haven't yet pulled it apart, grab a good* soldering iron and have at it. Hit the clock and lexicon while you're at it. (There are several good write-ups on what areas to check out.)
Old 03-28-10, 07:11 PM
  #127  
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You don't need an extra set of hands for the injector, took me all of 10 mins to do it. The primaries are a pain but the secondaries are easy.

I actually figured ut my beep as well, it was the Power steering computer, unpluged it and it stopped. So looks like i need a new PS ECU. have not hooked the PS up yet due to no belt so not sure if it works or not.
Old 04-01-10, 11:10 AM
  #128  
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Originally Posted by Texas_Ace
You don't need an extra set of hands for the injector, took me all of 10 mins to do it. The primaries are a pain but the secondaries are easy.
10 min you say, I better give myself two hours. I've learned from star-trek to over estimate my time, then the wife is happy that I did the work in a quarter of what I expected.
Old 04-01-10, 11:41 AM
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Originally Posted by BOFHMike
10 min you say, I better give myself two hours. I've learned from star-trek to over estimate my time, then the wife is happy that I did the work in a quarter of what I expected.
LOL, well if 2 bolts and 2 hose clamps take you 2 hours, then go for it. heck i didn't even take the fuel lines off, just took out the 2 mounting bolts, lifted the rail up high enough to get the old injectors out and stick the new ones in and bolted it back down.
Old 04-03-10, 07:29 AM
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Originally Posted by Texas_Ace
LOL, well if 2 bolts and 2 hose clamps take you 2 hours, then go for it. heck i didn't even take the fuel lines off, just took out the 2 mounting bolts, lifted the rail up high enough to get the old injectors out and stick the new ones in and bolted it back down.
Ahh, the cliff's/cole's note version! As I read the SM, I was under the impresion I needed to completely remove both the UIM and LIM in order to replace all 4 injectors. I'm all for easy.....
Old 04-03-10, 11:42 AM
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Originally Posted by BOFHMike
Ahh, the cliff's/cole's note version! As I read the SM, I was under the impresion I needed to completely remove both the UIM and LIM in order to replace all 4 injectors. I'm all for easy.....
Ah see, eearlier you made it sound like you were just replacing the seconday injectors, which are a piece of cake.

The primaries you do indeed need to remove the uppder intake manifold. Still not that hard, i have got it down to about 15 mins over time but it is a lot more involved.

Once you get the intake off though it is easy, the hardest part is keeping track of the vacume lines and bolts.
Old 04-17-10, 04:22 PM
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I replaced the 2ndaries. No joy. :*( I noticed the forward 6th port actuator looks like it's stuck again. That would account for power loss, but shouldn't stop rpm gain. The upper butterflies seem a bit stiff, I'm suspecting air starvation, or electrical malfunction.

I'm back to testing the electrical. Damndest thing, when I test drove the car it ran like a top. Didn't start acting up until I have driven about 80 miles then it was all down hill.
Old 04-18-10, 04:02 PM
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I'm battling a similar problem, but instead I suspect I'm going into limp mode, but can't figure out why. Computer is showing no codes. Car runs great initially, but after about a minute of so, check engine light comes on and WOT just kills the engine. Hoping to troubleshoot it further this week, but the frustration is that even through I'm getting a check engine light, I'm not getting any codes.
Old 04-18-10, 04:32 PM
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Check codes while the check engine light is on, there is some kind of code causing that light.
Old 04-19-10, 11:29 AM
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Originally Posted by bac22
I'm battling a similar problem, but instead I suspect I'm going into limp mode, but can't figure out why.
Interesting thought... My problems started after the coolant alarm went off. I think I've fixed the coolant problem, but I haven't had the battery completely disconnected since. I'll be pissed if that's all I have wrong.. My injector replacement resulted in a fuel rail leak, so I have to get new o-rings, but my old injectors may have been fine....
Old 04-19-10, 12:02 PM
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Originally Posted by Texas_Ace
Check codes while the check engine light is on, there is some kind of code causing that light.
I've tried several times to pull the code after the check engine light has come on, but all I get is the check engine light will flash off then on but nothing else after that. I'm wondering if the check engine light is on because I'm in limp mode...but what the heck is causing limp mode has me baffled.
Old 04-19-10, 03:59 PM
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Well never had a running S5 so sorry can't help you much there.
Old 04-19-10, 09:37 PM
  #138  
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While I was pulling my 2ndaries out for the 2nd time, I had a miserable eureka... my issue can't be my 2ndaires gone bad... IIRC - 2ndaries don't kick on unless there is load + 2800 RPM. w/o load I'm not able to rev over 4k.

What would happen if an S5 ECU was put into an S4? Are the pinouts the same? Would "limp mode" casue these issues? Wouldn't the injectors have to be replaced w/ high impedance? or have the resistor packs added?
I'm just tossing all my cards onto the table and seeing where they land. Tell me I'm insane and I'd understand.... I'm about a week away from buying another '87 NA to use as a doaner.

Wife has had enough of this poject.... She demands that I give her a ride in it so she can see what all the excitement is about.
Old 04-21-10, 08:32 PM
  #139  
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Tested my theory today and still no joy. Disconected the battery for two days, let the ECU clear itself. Started her up, still can't rev over 4k w/ or w/o load.
Old 04-23-10, 05:13 PM
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Originally Posted by BOFHMike
Tested my theory today and still no joy. Disconected the battery for two days, let the ECU clear itself. Started her up, still can't rev over 4k w/ or w/o load.

Hhhhhmmmm....with or without load...did you check for a clogged cat? I haven't had a chance to troubleshot my issue any further, but without load I don't have any problem going over 4K.
Old 04-24-10, 05:35 PM
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Originally Posted by bac22
Hhhhhmmmm....with or without load...did you check for a clogged cat? I haven't had a chance to troubleshot my issue any further, but without load I don't have any problem going over 4K.
Oh damn, I didn't think about that one. My car does not have the 2 pre cats, only an aftermarket cat + dual muflers. If I'm getting post detination in the cat - And I'm sure I am - it may be fubar. How would one go about testing w/o cutting the unit out? Since the 5/6 port actuators work of of back presure from the cats, shouldn't I see the actuators move at idel is the cat is cloged? Unless of course the clog preseeds the split air tube.

I really* didn't want to drop $700 on replaceing the exahust system. Such is life.
Old 04-28-10, 06:45 PM
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Quickest test I could come up with - start engine, let her settle on low idel, watch the aux ports and slowly increase the rpm. The ports were nearly wide open by the time I hit 2k rpm. Since they aren't suposed to be open till after 2k4, tells me I've got more backpresure from the split-air tube then I should. Would account for my lack of power and inability to hit 4k w/ or w/o load.

Question for everyone, I called nearly a dozzen places, cat replacement ran anywhere from $3k+ from Mazda, to $760 from Monro. Midas was about $850. Any comments one way or the other for the different muffler shops? My local general mechanic pissed me off last time I was in, think I'm going to leave this job to a pro.
Old 04-28-10, 08:20 PM
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I changed mine myself about 5 years ago, wasn't too bad of a job to do and the bolts came off reality easily even after being on for 15 years! Don't recall how much I paid for the cat, I think about $200 online somewhere.
Old 04-28-10, 09:05 PM
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Originally Posted by bac22
I changed mine myself about 5 years ago, wasn't too bad of a job to do and the bolts came off reality easily even after being on for 15 years! Don't recall how much I paid for the cat, I think about $200 online somewhere.
Unforunatly, the aftermarket cat on the system now was welded in place. I would have to chop most of the exhaust system, and I'm not handy with a mig.
Old 05-01-10, 07:27 PM
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Originally Posted by BOFHMike
... The ports were nearly wide open by the time I hit 2k rpm. Since they aren't suposed to be open till after 2k4, tells me I've got more backpresure from the split-air tube then I should. Would account for my lack of power and inability to hit 4k w/ or w/o load.
I drilled three small holes into the bottom of the cat. It's definetly reduced back presure, but not enough to make a differance on the max RPM the engine is acheaving. I was able to hit 4k rpm once while doing a test drive. Still have barely enough power to make it up the driveway (very slight hill).

My only positive note, I was able to stop a fuel leak by replaceing the seals on my 2ndary injectors.
Old 05-02-10, 06:15 PM
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Originally Posted by BOFHMike
I drilled three small holes into the bottom of the cat. It's definetly reduced back presure, but not enough to make a differance on the max RPM the engine is acheaving. I was able to hit 4k rpm once while doing a test drive. Still have barely enough power to make it up the driveway (very slight hill).

My only positive note, I was able to stop a fuel leak by replaceing the seals on my 2ndary injectors.
Can't say I've had a clogged cat before, but if you tap it with a hammer you'll hear the pieces moving around...I think? Might want to search the forum on that to make sure !

I'm beginning to think my problem might be a bad MOP that burnt the ECU .
Old 05-12-10, 06:33 PM
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Originally Posted by bac22
I'm beginning to think my problem might be a bad MOP that burnt the ECU .
Well that is my problem...just opened up the ECU and burnt resistor and cracked MP4501 module...off to ebay for a new (used) MOP and ECU...damn it!
Old 05-13-10, 08:37 PM
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Originally Posted by bac22
Well that is my problem...just opened up the ECU and burnt resistor and cracked MP4501 module...off to ebay for a new (used) MOP and ECU...damn it!
Damn, sorry to hear it. I think I finally pined down my coolant leak, which would effect the thermomax and BAC. Now I'm going to get back onto adjusting the TPS and DC idel. Hopefully this helps my RPM issue.
I've opened my ECU and didn't see anything obvious. I'm hopeing I'm not in the same boat.
-=mike=-
Old 05-14-10, 06:27 AM
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Originally Posted by BOFHMike
I've opened my ECU and didn't see anything obvious. I'm hopeing I'm not in the same boat.
-=mike=-
I doubt that's your problem since it's more of a problem with the S5 because the OMP is electrical rather then mechanical like the S4. Glad I found it, that's half the battle!

You might want to open up a new thread about your problem, since this one seems to getting a little long and most people probably are not paying attention to it anymore.
Old 05-14-10, 08:43 AM
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There have been several threads with cars that would not rev over 4000rpm. It turns out a LOT of them had no power to one of the secondary injectors plugs. Power can be checked by getting a meter out and backprobing the two secondary wires at the ECU with key ON. Should read batt voltage. No batt voltage on one of them means you've a open circuit to or from that injector.


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