help with 98 gt

[sn95gtvert]

im house sitting for a few weeks and my friends 98gt is here. his parents will pay me to work on it (he's mom is planning on owning it) it runs well rough i guess. bad throttle response poor acceleration just feels like a clunky pile to me.

i cleaned out the maf last night and it helpped a bit. im a 5.0 guy and dont know the first thing about these 4.6's so any advice would be awesome.

the speedo doesnt work, there is no cel, abs light is on and i think the 2nd set of cats are bashed out of the stock H pipe. cause the catback on it is just way to loud for a stock motor catback only car. its way louder then my full exhaust 5.0

 

[MustangChris]

well,

crawl under it and look and inspect the cats. that could explain the CEL and you could kill all three birds with one stone.

Bad cats = bad o2s.
bad o2s = bad input for computer.
bad input = bad performance and CEL.
2 new cats = fix everything.



BUT
ive never once heard of bad cats causeing bad enough issues to make a car "perform" noticably different. just MPG and CEL.

id do the basic checks, starting with the cats, the o2s, and getting the CEL read.
then move onto the air filter/PCV (simply because its the easiest) replace the PCV valve if its bad, and the air filter if its dirty.
then ignition. are the coils cracked? wires cracked or torn? spark plugs in good condition?
then fuel system. change the fuel filter. check the pressure at the rail.
also, check the vacuum lines. they are getting old and brittle and crack easily (you probably know, you've got them on your 5.0 lol.)


are their any other "symptoms" other than "poor throttle response" and the CEL? bucking? back firing? noises?

 

[sn95gtvert]

chris the is no check engine light. i bet it stores codes like my 5.0 so i'll see if i can get a scanner.
what should the plugs be gapped to on the 4.6? i'll go over the vacuum and check the pcv.

this thing is just in such rough shape i dont know where to start.

i feel like im trying to find a needle in a pile of needles.

 

[MustangChris]

my mistake, you did say no cel. i simply misread it.

lol, yea? those are the worst... worse than a haystack

id start with the basics.... intake, exhaust, spark, fuel.

speedo could be a bad gear. there is a write up on replacing it stickied in the "how to" section.

as for gap, im going 100% off memory because im at work, so someone else should chime in:

OEM spec: .054

 

[MidniteGT]

Air Filter, Coil packs, spark plugs(the gap .054 inch motorcraftsp-493), fuel filter, dirty clogged fuel injectors, and vacuum lines. most of what Chis said. I cleaned out my brothers tb and upper plenum on his 96 the other day and that made a slight improvement

 

[MustangChris]

i protest the cleaning of the inside of the TB and plenum on Ford OEM equipment. There is a sticker on it that specifically says "do not clean or touch the inside of the throttle body as it is coated witha grime resistant sumething er other.


i clean the outside of my TB (before the butterfly) but i dont open the butterfly when doing it.

thats a personal preference, made based off a sticker ford put on their equipment a decade ago... so take it for what it is...

i also suggest cisually inspecting as much wiring as you can. testing the battery, checking the water level in the battery, and cleaning the terminals.

 

[MidniteGT]

i protest the cleaning of the inside of the TB and plenum on Ford OEM equipment. There is a sticker on it that specifically says "do not clean or touch the inside of the throttle body as it is coated witha grime resistant sumething er other.


i clean the outside of my TB (before the butterfly) but i dont open the butterfly when doing it.

thats a personal preference, made based off a sticker ford put on their equipment a decade ago... so take it for what it is...

i also suggest cisually inspecting as much wiring as you can. testing the battery, checking the water level in the battery, and cleaning the terminals.

I wouldn't use carb cleaner or anything like that(on the inside). I did know about the protective coating. I used a clean rag on the inside. I guess I should of been more clear about that.

 

[MustangChris]

gotcha.

i use throttle body cleaner on other peoples cars. just not mine. lol.

 

[MidniteGT]

I actually didn't know about the protective coating till my brothers(mine doesn't have the sticker anywhere on it) and when I took his off I saw it. LoL at other peoples car.

 

[MustangChris]

yea, its still on my 96. and on the 5.4 one i bought from 330cube. so i assume its on all the modular motors...

and my parents car and my woman's car didnt have that stiker, so go to it. lol.

 

[MidniteGT]

also if you got a voltage meter check the voltage signal from the pcm to the IAC valve. It should be around 10.5 to 12.5 volts Just probe the wires of the terminals on the IAC.

 

[sn95gtvert]

ok so i checked the plugs, there motorcraft platiums gapped at .53-4 and they have a pretty good burn pattern. a little more carbon then i would like but whatever. this thing is a mess, none of the panels line up at all. the hood has been refiberglassed thats right, the entire underside of the hood is a wreck of fiber i dunno if i will be able to solve that problem. whoever painted it oversprayed onto everything. its even inside the trottle body. most of the wiring looms are white now the ac lines are just hanging loose. the radiator overflow is busted and just sitting ontop of crap loose. the fan shoud is zip tied to a rad hose. and the core support looks like it was hit with a 5lb hammer everywhere.

im going to have to upload pics so you all can understand just how much of a pile this thing is.

 

[sn95gtvert]

i think my 5.0 is jealous cause it flipped a sheep skin on me earlier, abs kicked in while i was cruising at 2k in 5th then my gauges went haywire and it died steering locked and i was flyin by the seat of my pants. but thats for another board

 

[MidniteGT]

Bondo on the hood? HAHA Chris he is going to have to clean that TB!!! Sounds like that car might be a money pit :sad5:

 

[sn95gtvert]

oh the pcv is still good, but really really oily. is that normal on 4.6's

 

[MidniteGT]

If you got good vacuum on the end of the valve you should be alright as far as the oil. Mine had a lot and I changed it out and my oil on it was a lot less. Motor looks like its been sitting there for a while. Looks like spaco*sp* on the tb(thats good for airflow :laughing5 lol. and I got a good laugh about you flying by the seat of your pants heheh.

But yea there looks like a lot of things that need to be done to that motor. i had to use my phone too look at them so it was hard to see stuff but when i get home tonight i'll relook at the pics. I would start with the cheap stuff first and then on.

 

[sn95gtvert]

uggg once i start working on one car all the others want some too. mine straigh up has to be fixed otherwise i might now make it home in a week or so.

and my friend that owns this white 98 has a black 95 that he wants me to finish for him. thats the one i'd rather be working on.
H/C/I 306 12 psi s/c front mount intercooler bov meth injected with a t56 and 4.10's
at least that one is fun to drive.

 

[MidniteGT]

Well if it makes you feel better evertime I fix one thing on my car something else breaks right after.

 

[sn95gtvert]

that doesnt make me feel better, it makes me think my car will shit out all the time. (knock on wood)
i know besides this abs malfuction my car is golden. only had to replace the 02's and the balancer in a bit over 2 years of owning it.

 

[sn95gtvert]

back on topic, the pig tail going to the drivers side coil is smashed one of the wires going to the pig tail about 4 inches before is is exposed. and one of the spark plug wires is busted where it attaches to the coil.