batmanfc

I've got an 88 TII with an s5 TII engine. I installed the engine around October of last year. I haven't had much time to really look at and get the engine running completely correctly until now. I still can't get the engine quiet right. When cranking the car, I have to turn it over a few times and once it cranks I have to make the car hold idle. The car will fluctuate about 200 to 300 rpm when I am holding idle, almost like it is a vacuum leak. Once the car gets to normal operating temperature the car will idle on its own around 750 to 800 rpm without any fluctuation. If the hood is up while the car is idleing the engine shakes horribly every few seconds like a miss, but I can't seem to hear a miss. All the emissions are removed, I've checked for vacuum leaks and couldn't find anything. I also tried putting the car into time today and the light didn't seem to show a miss and the engine is in time. When driving the car it has plenty of power when in gear slowing down the car will buck and if coming onto the throttle quickly it will hesitate and miss for a split second before coming into power. Also, the fuel injectors, throttle body, and tps came off of the s4 engine due it it wouldn't fit the harness othewise. I can't seem to figure why the car is doing this and have done everything I can think to come to mind.

Ryan123

iTrader: (3)

I would check The tps, do you have the s4 wire harness?

batmanfc

I've checked the TPS three times to make sure. Sorry, I meant to put that in the original post. The car has the stock s4 wiring but the engine is s5.

flipkc

Dead spot in the TPS. I have it too and I'm going to get a new one. I have the exact same problems.

batmanfc

I've checked the TPS several times and it seems to not have any dead spots in it when going from closed to WOT. I will check it again just to make sure.

texFCturboII

iTrader: (17)

how did you check for vac leaks? Have you inspected the turbo inlet duct for cracks?

batmanfc

Checked for vac leaks twice and couldn't find anything. No cracks on the turbo inlet duct either.

Jimmy2222

iTrader: (3)

Do you have S4 or S5 ecu?

batmanfc

I have an s4 ecu and wiring harness. The car itself is an s4 but the engine is an s5. I had to change the s4 TPS and fuel injectors over because the s5 TPS and injectors wouldn't fit the harness.

flipkc

Weird.

If it's not the TPS then I'm unsure.

Bump for the answer!

batmanfc

I will check the TPS again as soon as I get a chance to work on the car, but I'm almost positive it isn't the problem.

batmanfc

I also meant to ask what the point of grounding the green one pin connector when setting or checking the timing on our cars is?

flipkc

It's so that the car doesn't try and set values while you are adjusting things such as idle/timing.

HAILERS

Kinda odd the bit about the car bucking when you let off the throttle and "in gear when slowing down the car will buck".

The deal is this: when the RX7 is being driven and you let off the pedal completley, the fuel is cut to both rotors until the rpm drops down to around 1300 rpm (memory) and this is done for driveablility reasons (prevent buck from showing up). IF the throttle is let off just a tad......the fuel is cut to only the rear rotor (memory again, could be the front) and again this is for driveability reasons.

So I do wonder why your car bucks when you let off the throttle. Letting off completley or just a tad?

Then again the ECU has to know you let off the throttle (TPS and maye pressure sensor values also). I don't know what the problem is, this just caught my eye a bit and made me wonder a bit.

I used to backprobe the primary injectors with a meter to look at this fuel cut thing-a-majig before I bought a RTEK 2.0. Did it out of curiosity.

batmanfc

I wasn't sure. I have always done it this way but never understood the purpose.

At higher rpms like 2k and up it only bucks if I let off the throttle completely but at lower rpm under 2k it will buck if I let off the throttle slightly orwhen holding the throttle steady trying to maintain a lower rpm.

batmanfc

Could a bad coolant temp sensor cause these problems?

coolmike711

iTrader: (7)

I am having the same kinda issues too. I have my CAS turned almost all the way retared for the marks to line up. I did the whole TPS and vacuum leak check also. All emissions removed also.
Hope you can figure it out so I can fix my problem too.

batmanfc

My CAS is also almost all the way to to retard. I'm beginning to wonder if because my BAC is removed if that is the problem. Has yours been removed also?

flipkc

Next week I am going to get a new TPS and get it readjusted.

Forcefed Performance told me that it's because there is a dead spot in my TPS that the ECU is reading incorrect throttle values because the TPS isn't sending back the correct % of throttle.

I've researched the topic a lot and it makes sense...so I'll be getting it checked next week and hopefully it'll solve this problem.

Cheers!

coolmike711

iTrader: (7)

Had the BAC in same problem. Removed it same poblem
I really didn't think other guys were having this same issue.

I changed TPS twice. Recalibarated maybe a thousand times. Same problem.
Thought I had on the wrong pulley, changed that, same problem.

batmanfc

[QUOTE=coolmike711;10120158]Had the BAC in same problem. Removed it same poblem
I really didn't think other guys were having this same issue.QUOTE]

I was kind of beginning to think because my BAC is removed that it may be causing the problem. I'll still give it a shot but I'm guessing now that it won't help much. I was also beginning to think I was the only person with the problem. I have asked and searched and can never find the same problem, let alone the solution to the problem. Hopefully now that I know I'm not the only one, one of use can figure it out haha.

coolmike711

iTrader: (7)

I am so pissed that I am actually putting together the S4 engine that blew so I can put it back in the car.
I have tried everything I can think of and still no fix yet.
If anyone has a suggestion please let us know. There maybe something somewhere I missed.

flipkc

I don't think it's the BAC because it has nothing to do with the throttle?

Honestly I think it's either the TPS, a vacuum leak, or the motor.

I was guaranteed it was the TPS...so hopefully the new one I'm getting is going to solve this issue.

coolmike711

iTrader: (7)

Do you have a S4 car with a S5 enigine in it?

flipkc

I have a JDM S5 T2.

I think my BAC is non-adjustable...