hesitation/ miss issue 89 vic

[73nancy]

ok guys asked about my problem with my 89 vic awhile back and so things have been done but no change. my issue is i have a hesitation feels like a miss on acceleration. the car does have a t-5 swap.

things i have done include new plugs/wires about a year ago. new cap rotor,tps,cleaned throttle body,iac,egr valve.

ran the codes and they are some for the air pump which i have the crossover pipes blocked off dont know if that can effect anything. but the other code is #13 which is cannot control low rpm. i cleaned the throttle body and iac thinking it would help. it did help some gave me power at the top end of the rpm range which was hard to get before, but now the car idles at 1500 wont come down off from that. the exhaust is puffing at idle but dont know if that becuase of the punched out cats and the slight exhaust leak i have or if its missing at idle.

the car of course has a t-5 swap and doesnt like any high gears lower than 2k or else it will buck. im wondering if i need a mustang computer but dont know if any mustangs came with a non ho with a 5 speed with speed density.

any help would be great need to get this problem figured out before i go home for the summer the hesitation/miss is a new problem where the bucking in high gear is a old one. thanks ryan

[86VickyLX]

ok guys asked about my problem with my 89 vic awhile back and so things have been done but no change. my issue is i have a hesitation feels like a miss on acceleration. the car does have a t-5 swap.

things i have done include new plugs/wires about a year ago. new cap rotor,tps,cleaned throttle body,iac,egr valve.

ran the codes and they are some for the air pump which i have the crossover pipes blocked off dont know if that can effect anything. but the other code is #13 which is cannot control low rpm. i cleaned the throttle body and iac thinking it would help. it did help some gave me power at the top end of the rpm range which was hard to get before, but now the car idles at 1500 wont come down off from that. the exhaust is puffing at idle but dont know if that becuase of the punched out cats and the slight exhaust leak i have or if its missing at idle.

the car of course has a t-5 swap and doesnt like any high gears lower than 2k or else it will buck. im wondering if i need a mustang computer but dont know if any mustangs came with a non ho with a 5 speed with speed density.

any help would be great need to get this problem figured out before i go home for the summer the hesitation/miss is a new problem where the bucking in high gear is a old one. thanks ryan

There is no non HO mustang with 5 speed. Speed density or MAF.

When you unplug the IAC, does the idle go down? And if so what rpm does it go down to?

[73nancy]

doesnt really change much. went back out and fired it up and it didnt idle high it seems like it does after you drive it. it goes up to 1500rpm but just now it stayed at 1000 with or without the iac

[86VickyLX]

doesnt really change much. went back out and fired it up and it didnt idle high it seems like it does after you drive it. it goes up to 1500rpm but just now it stayed at 1000 with or without the iac

That's still a little high. You might just have some vacuum leaks that you need to address. Check for vacuum leaks first. Then if there aren't any, then someone messed with the Screw on the throttle body. And you'll have to adjust until it's idling around 750rpm with IAC unplugged.

[73nancy]

after adjusting the idle down will that tend to help with hesitation issues when under a load with the iac pluged in. i just ran the car with it unpluged to see if it acted diffrent and it feels like it has more power down low then its ever had pulls real hard at wot but still hesitates under load partial throttle. i have never touch the idle adustment any but it did idle at 900 or so before i cleaned everything out but it did run better after the cleaning thats when the idle went up.

[86VickyLX]

after adjusting the idle down will that tend to help with hesitation issues when under a load with the iac pluged in. i just ran the car with it unpluged to see if it acted diffrent and it feels like it has more power down low then its ever had pulls real hard at wot but still hesitates under load partial throttle. i have never touch the idle adustment any but it did idle at 900 or so before i cleaned everything out but it did run better after the cleaning thats when the idle went up.

The person before you probably messed with that screw because it was idling too low. Gunked up with the crap you cleaned out. Setting it there will make the engine run better. I'm not saying it'll fix your hesitation.


This is what I want you to do, so we eliminate stuff as we go. First, set the idle at about 750-850rpm with IAC disconnected. When that's done, shut the engine off, put the key in run, but don't restart it. Now set the TPS at 0.900V or under it. You'll need a voltmeter on the green wire of the tps and ground when doing this. Loosen the screws holding TPS and move it until you get to .900v or close to it. But make sure it's under .900v. The computer likes to see it around 0.900v. This will help with throttle response. Plug in your IAC if you haven't already done so. And start the car. Drive it and see how it acts then.

Just thought of this...

Is the Vehicle Speed Sensor hooked up on the transmission?

If not it could cause some weird problems too.

[73nancy]

ok i will try and do all that tom at some point during the day.. on the t-5 i have the speed sensor in there not sure if the factory wires are hooked up but the speedo works. ill check to make sure the pigtail is hooked to the harness as well. one question on the tps do u need to oval out the holes or do they have enough play to move around, seems pretty snug on the two bolts.

[86VickyLX]

ok i will try and do all that tom at some point during the day.. on the t-5 i have the speed sensor in there not sure if the factory wires are hooked up but the speedo works. ill check to make sure the pigtail is hooked to the harness as well. one question on the tps do u need to oval out the holes or do they have enough play to move around, seems pretty snug on the two bolts.

You should have enough movement to get the sensor where you need it.

[73nancy]

ok well just went out to adjust the idle down and all hell broke loose. the adjuster bolt snaped off so now i have nothing there.. car still runs but the idle droped down to around 600rpm with iac pluged in. dont know what to do now half the bolt is still in there so i will need to drill it out then re tap.. the old one the kid must have known it was froze up because u can see grinding marks where he ground it down. not sure if it the stock bolt it has a chrome'ish end size 5/16.
im guessing that 600rpm is way to low at idle for a 5 speed. i know old carb stuff that about right not sure on this efi stuff.

[Ike Clanton]

Mine has a very brief hesitation from idle to when I initially dip into the throttle just when the throttle plate first starts moving, as in just the briefest of the brief, just a little stumble, usually when not fully warmed up. I always assumed the IAC was just dirty. I bought one used to clean and install, but just haven't done it yet.

[86VickyLX]

ok well just went out to adjust the idle down and all hell broke loose. the adjuster bolt snaped off so now i have nothing there.. car still runs but the idle droped down to around 600rpm with iac pluged in. dont know what to do now half the bolt is still in there so i will need to drill it out then re tap.. the old one the kid must have known it was froze up because u can see grinding marks where he ground it down. not sure if it the stock bolt it has a chrome'ish end size 5/16.
im guessing that 600rpm is way to low at idle for a 5 speed. i know old carb stuff that about right not sure on this efi stuff.

EFI is 650-750. But that's with Automatic transmission. I would think it's too low for a manual application. Not sure. How does it drive now?

[gadget73]

Mine has a very brief hesitation from idle to when I initially dip into the throttle just when the throttle plate first starts moving, as in just the briefest of the brief, just a little stumble, usually when not fully warmed up. I always assumed the IAC was just dirty. I bought one used to clean and install, but just haven't done it yet.

try unhooking the egr valve. if it fixes it, pop the cap off the egr vacuum regulator, remove the foam (and dispose of it if its all crumbly) and shoot some wd40 down the hole to see if that fixes the problem. Might also be worth checking the codes. Sometimes you'll find something related to the egr valve or TPS that explains a hesitation issue.

[73nancy]

ya car drives the same still has a hitch in its step like a miss around 1/2 to full throttle. the codes were code 13 cant controll low idle before havent check it again might do that tonight. the car stalls now though its fine cold will idle but when it gets off the cold idle it will surge then stall. can still drive it but if i dont keep on the throttle when turning or coming to a stop light it will stall. i cleaned the egr valve out but the end of it where theres a cap and two screws one i could get out so i left it. havent been able to tune the tps either tried getting a reading off the green wire with just the key on and didnt get anything. does it get power with the key or does the car need to be running? ill go out a read the codes again see what i get. i will also unhook the egr plug see what happens

[73nancy]

just went out checked the codes. got code 12 cannot control high rpm it was code 13 before i broke the throttle stop off. i also have code 21 now which is ect out of range dont know what that is. i also unpluged the egr it wouldnt idle only way to keep it running was to stay on the throttle manually. so my guess is i have to get this throttle stop fixed then go from there. any other ideas guys. thanks ryan

[gadget73]

21 probably means the motor wasn't warmed up. if thats the case, ignore it.

12 and 13 at the same time usually mean the IAC is no good, but the broken throttle stop screw is not helping. Fix that and see what happens.