Massive lag for a second at around 5300 RPM.

[Sean]

It just started occuring when I got back here to Boise. This is really the first issue I've had with my stroker since I built it.

The only thing I've checked so far was to see if it was the filter, since it had been WAY long since it had been cleaned. However, that made no difference.

When accelerating at fully throttle, mostly in second, but there in all gears, I notice a huge amount of lag around 5300 RPM. It's almost as if someone slames my brakes half-way for a second then lots off and I continue to accelerate at the same rate. It's very weird, and drives me insane.

I haven't checked anything else yet, but I will be doing the following:
- Switching AFM with another (since I have access to two other ones)
- Checking plug conditions, possibly putting in new ones
- Adjusting valves (needs to be done anyway)
- Checking condition of ignition components (coil, wires, etc etc)

The reason I'm posting is because, could the following items be a cause of such a reaction as well? (ONLY at that RPM)
- dirty fuel filter? (only has less than 10,000 miles on it)
- bad crankshaft position sensor? (this was reused from my previous motor)
- old spark plug wires?


Some things to note:
- When I put together my stroker, my throttle body was cleaned VERY THOROUGHLY. And I checked it 1000 miles ago, and it was clean as can be.
- AFM has probably 190,000 miles on it - originally from my parts car


So...does anyone have any hunches as to what it is? Also, what things should I check if none of the above thigns I'll be doing remedy the situation?

Thanks! :)

-Sean

[Nick325is]

Mine did that a couple years back. It turned out that the AFM was the culprit. Do you only experience the problem at WOT?


-Nick

[SpecM]

-Mine does this @ WOT @ 4-4.5k

[HST]

AFM or injectors?

[Sean]

I only notice it at WOT, that is correct.

I'm hoping it's the AFM. Cause, that would be swell if so! :)

Man...when I have the money, I really wanna do a piggyback or standalone so I can run a MAF. :D

I'll let you know what my tests show!

[SpecM]

-I was thinking... maybe a clogged-up cat?

[Mystikal]

Man...when I have the money, I really wanna do a piggyback or standalone so I can run a MAF. :D

No need, MarkD has an MAF chip releasing soon, pending testing on my car. It's an easy as installing his MAF in place of the stock AFM, and swapping chips.

-Jay

[Sean]

-I was thinking... maybe a clogged-up cat?

That could be the case if it weren't for the fact that my cat has 10,000 miles on it, and is a free flowing catco cat. :D

UPDATE:

Tested my car with my brother's AFM. It gave me WORSE symptoms. NOW when I hit about 5300-5500, it's like I'm slamming the revlimiter - but only at WOT. He had an identical problem, which was fixed when we changed his crankshaft position sensor. Any takes on this? His problem is gone, and all we did was change his crankshaft position sensor.

Mine is original, and has between 190,000 and 230,000 miles on it - so I wouldn't be surprised if it was crapping out on me.

-Sean

[AlarmedBread]

Could be the CPS, try checking the wiring to see if its frayed, or see if you can ask someone nicely to borrow one to try, I've got a couple spares that are good. Too bad you aren't closer.

I had the same problems, it turned out to be my ecu going bad, I swapped every possible part before trying a diff. ECU. I'd reccomend trying the ECU first!

I have a maf system for 173dme FS if you really want one, pretty cheap too!

[Sean]

Another update just to close up the issue. Installed the new Crank Position Sensor, and it's fixed! There was one second gear pull that I thought it wasn't, but I did like 5-6 more last night, and it's DEFINITELY better! It seems to pull harder than before up high too - but who knows, that could be a placebo. :D

[AlarmedBread]

Cool beans!

Another thing to do is unhook your battery to clear the ECU, it may have learned some bad habbits from the faulty cps. You've probably already done this but hey ;)

[Sean]

Boy...was I wrong.

A week into driving it...it does it, and worse.

Between 5 and 6 in all gears, the car jerks back and forth, like it's KIND OF hitting a revlimiter, then it goes up about 200 rpm and does it again. ONLY at full throttle.

I'm really at a loss here. A buddy of mine thinks it's ignition related...and I tend to agree. However, it could be fuel related too. Since I have bigger injectors (17# as opposed to 14#) (S50 injectors), at full throttle, it's most likely running rich - since I don't have an adjustable FPR nor the M30 AFM on yet.

Could running rich cause this to happen? Could my plugs be fouled? I'm going to pull them out and take a look tomorrow at em.

I checked resistance in the plug wires, and there's none in em. I'm going to try switching out my coil, and see if that does it. It's definitely not the cap or rotor...I looked at them, and they were in amazing shape.

Idea...suggestions...bring em on!

[nando]

running rich wouldn't do it drectly. you might get bad gas mileage, but that's about it. I doubt it'd run very rich with 17# injectors anyway. do check your plugs though, since it's easy enough.

get a digital multimeter and test all those sensors etc. one by one. TPS, coolant temp, AFM, etc. also check the round connector under the throttle body for corrosion (and if it's there, check out the coolant hoses on your TB).

[Yakinho]

My friends M30 in his e28 does the exact same thing. No idea.

[Sean]

running rich wouldn't do it drectly. you might get bad gas mileage, but that's about it. I doubt it'd run very rich with 17# injectors anyway. do check your plugs though, since it's easy enough.

get a digital multimeter and test all those sensors etc. one by one. TPS, coolant temp, AFM, etc. also check the round connector under the throttle body for corrosion (and if it's there, check out the coolant hoses on your TB).

What readings should I get on these?

At one point, one of my coolant hoses connected to the TB were loose, and started leaking. Got it tightened, and it was fine. It's possible that the coolant the leaked corroded a connector, eh?

My friend last night suggested the TPS. I might just try the other one that I have.

Thanks, Chris!

-Sean