Surge while holding accelerator steady?

[bmxrider154]

no surge at idle, fixed that (injector o rings), but surges when i hold the accelerator steady. pulled 12, 13, 14, 25 out of ecu, which are all included in MAS except tps(14). My theory is fuel pump, plug wires, or a vaccum leak. WOuld check all those but dont have the car yet. 90 gsx. Thanks

 

[realhp=turbo]

Mine does that too. Is urs stock? Im thinking that its my factory boost control solinoid but Im not sure.
mike

 

[bmxrider154]

yeah its completely stock, check ur spark plug wires and that might be it. I dont have the car yet so i havent tried much. i do need a new MAS so im going to try that first along with the wires.

 

[realhp=turbo]

I did buy new wires it didnt help.

 

[GORBS88]

Egr, try unhookin it....if it is a part throttle hesitation/buckin could be the problem...

 

[bmxrider154]

i tried the mas out of my other car, didnt help. Im just going to get it towed home and fix it here, much easier. I will keep you posted. Does urs only do it around 2k rms? that is when mine does it.

 

[realhp=turbo]

Yea it feels like it pops open at 2k and then again at 2,700 and then full boost at 4k. Thats with the throttle at 25% from go.and at 4k I drop the throttle.

 

[Spool'n Spyder]

Mine did that because the tps was slightly out of adjustment. As a matter of fact, I just fixed it two days ago.

 

[bmxrider154]

next im going to try egr, isc, and i dont know what else, its weird.

 

[steve]

Have you found and fixed the CEL related problems? Don't do too much else until you do.
The TPS by itself will cause bucking.

Steve

 

[bmxrider154]

there is a few cel's, tps, barometric press., and the other two that are in the MAS.

 

[steve]

there is a few cel's, tps, barometric press., and the other two that are in the MAS.

Right, so track those down before playing with the EGR or ISC. If you have access to a logger check those sensors values and check your ECU to make sure you haven't fried the +5 sensor power of ground.

Steve

 

[bmxrider154]

i know it isnt the MAS, i took it out of my other car and didnt help. tps could still be it, i havent adjusted it to perfection yet. i was just going to swap the isc and egr from other car but i might sell it here in a minute. thanks. i will pull ecu out real quick

 

[bmxrider154]

ecu doesnt look bad, capacitors have been replaced and looks clean. how can i check the ground?

 

[steve]

http://www.vfaq.com/mods/ecu-harness-1G.html

Check to make sure that there is continuity between pin 101 and 24.
Remove the ECU board from the case and check the back side to make sure you don't have and discolored or burnt traces. Also look closely at the chips on the top right of IC101 for burning.

The TPS, MAF AF, IAT, and Baro sensors all share the Sensor +5 that comes out on pin 23 and sensor ground on pin 24. The sensors can be fine but not getting power or ground.

Steve

 

[bmxrider154]

continuity is 0.4 ohms. there is a little bit of glazing or clear film on IC101 and also a little bit of cracking on top right. not burning on backside. would the ecu out of my 90 laser fwd turbo 5spd work on my 90 gsx 5spd?

 

[steve]

continuity is 0.4 ohms. there is a little bit of glazing or clear film on IC101 and also a little bit of cracking on top right. not burning on backside. would the ecu out of my 90 laser fwd turbo 5spd work on my 90 gsx 5spd?

The resistance between the two should be 0 ohms.
The conformal coating cracking arounf the transistor and 8 pin chip in the upper right corner of IC101 isn't a good sign. Can you check the voltage at pin 23. It goes to the TPS (pin 1) and MAF (pin 4) if it's easier to measure there.

Yes, the MD128625 will work in place of the MD145903. It's not a perfect match but it will work. Are either EPROM?

Steve

 

[bmxrider154]

fixed, steve you are a genius! i just swapped ecus and that was it. Thanks

 

[steve]

After a while you start noticing common problems. I haven't yet figured out what causes the failure. Did you change an O2 sensor or let the MAF or TPS connectors get soaked lately?

Steve

 

[bmxrider154]

no i just got the car actually, but not too happy right now. I just got the hood to the windshield, forgot to latch the hood....pissed! how hard is it to change a windshield?

 

[steve]

Oh shit, that's an expensive oversight. Sorry.

 

[bmxrider154]

yeah tell me about it. do u know how much it might cost me to get one installed?