limp mode?

[kevo]

hi all, took my m52 for it's first test drive today, bugger me it's rapid haha. i'm running a 3.91 diff and an e30 m20b25 gearbox, with lightened flywheel and it feels short but lovely.
one issue i have though is that when it first starts it revs up freely, but when it 'loads up', i.e like when it's revved hard in a higher gear like third it stops revving over 5200-5500 rpm. once it stops revving over this range i have to switch off the engine and restart but then it does the same thing again in the higher gears?
is there a limp mode on these lumps? or is it something like my vanos playing up?
when it is in this 'non revving state' it goes like stink still up to that point, it just feels exactly like a rev limiter?
any ideas?
cheers
Kev

[DanThe]

Could be a few things that will put it into limp mode, have you got lambdas fitted and wired?

[kevo]

yes they are on and wired in, although it does pop slightly on decelleration so it may be a little rich? do you reckon the lambdas could be faulty? i have another pair here to try?
cheers
Kev

[nickso]

hmm , mine pops like mad on overrun, doesn't cut the revs though.

[e30-EVN]

Faulty cam sensor maybey kev.....

[e30-EVN]

Mines been running with the lambda's unplugged for a bit as they are both shagged but she still goes to the normal limiter. Runs a bit rich but doesn't stop short of the limiter

[Nas80]

abs input required - this is the nanny state rev cut you have. - revisit your wiring diagram and run a wire from the speedo sensor to the abs wire.

or if your e30 has abs then you should use that wire off the c101.

your going to have to reset / clear fault codes off afterwards.

if you got this far you wont need me to tell you what pins do what - i dont remember off the top of my head lol.

[e30-EVN]

Not necessarily!!

My first loom made by danthe came to me without abs power supply.... I ran it around for a few days and the car behaved brilliantly no issues whatsoever. (Appart from no abs of course) but not a hint of kevs problem!

Faulty lambda burnt the loom out so when I requested a new 1 from dan I had him put the abs power supply in and no change.

I would put money on it being sensor related

[kevo]

i'll have a look at the abs sensor thing then good thinking, i think it's MAF related for some reason though don't know why though. i'll be having a good look on saturday cheers for the ideas guys. did you sort your lambdas out ant?
Kev

[e30-EVN]

they haven't arrived yet kev, he cant get to the back one so hopefully he can rip the engine out today and send em down to me recorded delivery........

the car is very drivable on default values (lambda's unplugged) but i cant barely keep up with the consumption! haha. but id rather it run slightly rich rather than lean!!!

[Nas80]

wouldnt think it would be MAF id have thought a dodgy MAF would make the car run like crap rather then a 5500 rpm cut.

At least it would on an obd1 not too sure if that triggers nanny state on obd2.

[Green]

wouldnt think it would be MAF id have thought a dodgy MAF would make the car run like crap rather then a 5500 rpm cut.

At least it would on an obd1 not too sure if that triggers nanny state on obd2.

Saying that when I accidently fitted the wrong MAF to my old xr2i, the revs halted at 4k and the acceleration was awful.

Get some diagnostics on it, will make it a lot easier

[Nas80]

Aye. Thats the only sure fire way to know tbh.

[wullie325i]

i would go with lambda as i had a faulty one that also ended up melting the loom.

seems quite common now that alot of people have done the swap.

[wullie325i]

melted right next to the diagnostic socket and nearly went into the car side of the loom too

[kevo]

i've just bought a cheapy obdII reader so i'll plug that in and see what i get, is there a way of testing a lambda?

[craigieeb]

Ididnt think the lambda caused "limp mode" ..?
i would look at cam sensor, crank sensor and.....
how did you wire up the speed signal sensor?

[kevo]

is the speed signal sensor the one that goes to the abs wire? i'm not sure whats been done with this and after looking at your previous post about limp mode it's the first thing i'm going to check.
Kev

[kevo]

right i've just checked my wiring and i have a red yellow on the car loom side (hooray not brown), and a red yellow on the e36 engine loom side. however, the engine loom side isn't connected to anything? what should it go to i'm a little confused?
cheers
Kev

[kevo]

right, pin 20 on the c101 is no issue, i've found that one. as i've paired down the loom to only what i need i assume i need to connect the 'engine speed output' pin from the ecu to the abs power on pin 20. does that sound right? what does it do exactly then?

[kevo]

well i wired the speed sensor into pin 20 and it made no difference. boo. the same black wire though goes to pin 9 also? should this be the case? the car feels like it's missing also so i'm going to test the coil packs and lambdas and make sure the lambdas are the correct way round also.

[Nas80]

Engine speed is your revs. abs you need to look for mate.

Also if its missing make sure u have your lambs plugged in the right way round too.

Which diagram did u use when wiring it up?

[Nas80]

also you have to clear the error off / reset ecu afterwards.

[e30-EVN]

dont have to delete codes on an m52, diagnostics are far more advanced than that of an m50!

for the record kev the front lambda plugs into the back plug and back lambda into front plug.......
ive been running mine with both lambda's ''unplugged'' for a few weeks now and it still revs to the limiter. it runs on default values and over fuels when foot is hard down but it is still very drivable and i have not once had it rev cut!
i also plugged them in the wrong way around when i first put the engine in and again this did not cause a rev cut, it just felt a bit lazy.... did not miss either!

have you tried the cam sensor kev? thats where my money is..... and for the miss maybey the plugs and coils?

the m52 loom is not like the m50.... by this i mean you cant get any of the plugs (cam and crank sensor ect ect) the wrong way around. each plug has a different pattern

Ant

[kevo]

hi guys bit of a marathon day, i have an intermittent misfire now too. i've...
swapped the coil packs for two known good sets and it's still there
changed the brand new plugs for a known good set
changed the cam sensor for a known good one
changed both lambda sensors to known good ones
checked the pin data on the ecu to the relevant positions
added the speed signal (black wire) to the abs wire in the c101 loom
put a diagnostics code reader on the car and cleared the codes and read them

i still have an intermittent miss. as i had a bit of an unexplained miss on my m20 b25 engine i'm beginning to think that it's something breaking down on the original untouched side of the loom off the e30. the car will pull like a train for one part of the rev range randomly then sputter and miss a moment later, and it pops alot too.
are there any other relays in the car to control the engine? as theres a blue one under the glovebox that i'm going to look at and is there a crash sensor cut out or something in the wiring somewhere?
cheers for the help again guys
Kev

[kevo]

breaking news, man has been found decapitated. oops wrong story, anyway i took my lambda relay out and swapped it for a spare relay and the problem dramatically reduced. i had full speed for a bit but it intermittently cut power a bit still and popped slightly, then full power etc etc. anyway i'm going to look at every part of the wiring to do with the relay base tomorrow and trace the wires looking for a dodgy connection/joint and hopefully that'll be whats wrong.
to be continued....
(but hopefully for not much longer)
kev

[kevo]

loving this job honest. been through all the wiring and the problem appears to be to do with the lambda sensors of some description, i have swapped them for a known good pair and pinned out all the wiring and it all goes to the ecu as it should etc. however i do have an error. there are four wires from the lambda red/white, brown, yellow, black.

red/white is the 12v feed from the 02 sensor relay and is present.
yellow has 4.6v
brown has 4.6v
black has no voltage to it.

as far as i see it black should be the signal wire which should return between 0 -5v depending on the mixture condition.

yellow should feed 5v to the 02 sensor

red/white sould be switched live 12v power

brown should be an earth which is switched by the ecu

i'm missing a switched earth from the ecu and i have two 5v feeds when i should have one? i'm thinking my ecu is broken/damaged as the pins on the ecu correlate to the lambda sensor cables and they don't seem to have continuity to anything else?
can anyone confirm if i should be getting the readings i suspect i should?
cheers
Kev

[DanThe]

Sounds a right mess. You should have bought a loom off me Kev

[kevo]

haha, yes bit of a mess, the trouble is that i have a full sequential gas kit fitted too which the loom for is bigger than the e36 one! and they're spliced together an a million places. and as it came out of a running car i thought it'd go straight back in i'm getting near the end now though at least i know it's to do with these lambda readings so i'm going to try and prove whether it's my ecu or the wiring in between next.
kev

[kevo]

right then, my running issues are over, woohoo. i had a few faults in total, the limp mode ended up being that the abs signal wire wasn't connected which is pin 9 on the x20 plug (the e36 version of the e30 c101 plug) and it comes from pin 15 of the 88 pin ecu plug and connects to pin 14 of the e30 the (blue and yellow wire in my case, but i've been told it can be black/white also).
the other running issues were the ecu which i had which was broken and stuck in limp mode for some reason, although it was fine when i removed it from the running donor. so after changing the ecu this problem went away.
also i had a dodgy crank sensor which again was fine previously but for some reason decided to become intermittently faulty when being transferred.
also one of my lambda sensors was dying a bit and intermittently giving me rich lean condition.

anyway i've finally got to the end of that bloody saga, haha no wonder it was so hard to find when it ended up being four different problems, hence the reason i thought it was my wiring which turned out to be fine in the end. typical.
cheers for your help
Kev

[glenn]

[kevo]

your calipers were started yesterday by the way glenn, i've made a set already but i'm not sure they were strong enough so mark two is in progress. should be done within a week.
Kev