hello guys i do not post here a lot. do more lurking and reading taking in information because turboing my car seems hard for me to wrap my mind around. well atleast the tuning and all the things you have to pay attention to detail on.

ANYways i have a 92 1.6 miata and i got it cheap had 190k on it and the engine smoke when i drove. not too bad. but i bought a newer less mileage engine with 60k on it and swapped it in this last weekend. and when i Went to start the engine it started right up then started surging like will not idle lower then 2k and if you give it gas it just starts climbing and dropping. with the gas still pressed steady.

i switched injectors and cas to this motor from old one and throttle body because this engine was out of a auto and my car is a 5 speed. but did some searching and came up with nothing like this. herd of the IAC causing idle problems but nothing like this.

like its trying to be a ported rotary. it will rev and drop. but not at low rpms just seems to act like it is missing. but no vacuum leaks or anything i have no clue where to start.

any help or a direction to take this in would be much appricaited. you guys here at miata turbo seems to know your way around these cars pretty well so i figured i would ask here. thanks

 

Is your MAF/AFM hooked up?

Sounds like a typical vac leak to me.

 

see i checked all vac lines and nothing changed it. and i did start it first without the afm hooked up then i shut it off and hooked it up then started back and its like surging reving for like two seconds then droping then repeating.

 

Check for vacuum leak around the injectors. With the car running, spray some brakleen (brake parts cleaner) around each injector individually and see if theres a change with the way the motor runs.

 

ok being that it is almost 2 am i will do that first thing in the morning. i hope it works

 

yeah man its either a vacuum leak post tb or there is a great posibiliity of a leak if you reused the stock intake manifold gasket, either way spraying flamable liquid at suspected areas will show you where the problem is. Is the AIC hooked up or blocked?

 

Double-check that the CAS is oriented correctly and it's tight.
Check your timing and if it's out, place a jumper wire on TEN and GND in your diagnostic box as you would do to change the timing.

 

+ 1 on vac and CAS orientation. Double and triple check your vac lines, I've had one right before me that I missed until the third time I checked it.

 

well tried the brake clean thing not of the injectors are leaking. and checked all vacuum hoses three times today nothing is out of place. checked firing order. it did not surge as it did yesterday now it just will not go below 2000 or will rev to 3000 and stay.

i do not get it. as for the cas i have played around with different settings on it to get it to run smoother. but i have never messed with the diagnosis that would be a first for me. but the only adjustment i have is the cas correct?

there is no other varaible in the timing on a stock car correct? ? ? cant figure it out its pissing me off

 

If you've never played with jumping the TEN and GND in the diagnostic box, do a search about "timing advance".

Not sure if I missed it, but have you mentioned anything about how your car drives? ie. does the RPM go up and down like it is when giving it gas when stationary?

Perhaps it's a fuelling issue, or to be price LACK of fuel.
Two things spring to mind:
1) fuel filter need replacing (easy)
and/or
2) In-tank fuel pump need replacing (difficult)

Perhaps whenever your engine is dropping RPM's that's when the fuel is not getting to it properly.

Go for a drive and give it a boot-full now and again. If it struggles at high RPM's (over 4,000RPM) then fair chance it's fuel related.

Actually, before you do anything too tricky, rule-out the simplest things;
replace all your spark plugs and leads, and check your air filter.

 

ok guys i think i found the problem went out today and started it and it did its whole little spaz thing. and playing with the throttle and it felt really sticky so i took the tps off and parts fell all over.

so somewhere in all this my tps got destroyed i never removed it from the throttle body just swapped them. so i guess it was close to this driving it around idk . going to replace and report back.

thank you guys for all the suggestions and help so far

 

Im glad you have a spare TPS cause those things arn't cheap on the 1.6's!

 

You have a vacuum leak; specifically somewhere between the AFM and intake manifold gasket. Find it.

 

well i figured vacuum leak too because i have had problems like this before also. but this engine was complete with intake and everything on it. all hoses. but i went over all of them and made sure they were good. and they are all in great shape not brittle or anything replaces some hose clamps on the iffy ones.

had to order a tps sensor so waiting until tom for it. it was 60.00 so hopefully that is my only problem . but i am dieing to drive this car. both miatas i have owned have had close to 200k on them this engine is 60k or so and i put a cheap ebay f1 stage 3 clutch kit in it. ( the kid i bought this car off of for 300 was drifting it. )'

so i am trying to bring this car back from death so far with everything else i have done the engine and clutch and hubs/bearings/bushings/seats/ bla bla keeps adding up but likeing the car more and more

 

you could unplug the TPS and the computer would hardly care.

the only way to increase your revs is to ingest more air. 2K idle = too much air = leak.