[adsport]

Hi all, i've just plunged myself into the world of vitara's, i bought a 93 efi auto LWB about a week ago. amidst other issues which have arisen with the car after buying it there is one very curious thing that stands out.

The car appears to have a misfire from 1200-1800RPM under load. it's honestly quite weird how it does it. it genuinely SOUNDS like a misfire but i am not convinced. the first thing that i did was replace the spark plugs, and the leads. the issue became a bit less prominent but it was still there. a few days later my new cap and rotor arrived, fitted them tonight and the issue is still there. ive had the car up on the hoist to load it up in drive and to check things underneath. the driveline seems to be pretty rattle free and solid although the tailshaft is slightly not true straight and sometimes a tapping noise comes from INSIDE near the yoke. the misfire sensation ONLY occurs if the wheels are turning.

if you free rev the motor, no misfire
if you put the car into L,2 or D holding the brakes the doesnt misfire
if you lean on the brakes and get the wheels to turn it doesnt seem to do it (requires you to stall it up obviously, but yes it will do what scientifically qualifies as a standstill for .4 seconds)
with the car on the hoist, brakes on for loading up as you get into the rev range it will miss.
if you take off from standing with anything under say 70% throttle (not gunning it) it will miss
if you are cruising along at any speed and the revs are within the range it will miss.


now those are pretty much all the times when ive managed to force it to happen, im becoming more and more sceptical that it is an actual ignition problem as i have pretty much overhauled the ignition system. the motor sure sounds like it is missing and the sensation while it happens is that of a driveline vibration. timing without diagnostic connector bridged is at 12 degrees. ive just learned how to bridge the diagnostic connector so i will reset the timing and see if the ecu will spit out any codes tomorrow.

I am planning to get another tailshaft to replace the bendy one that i have, which has maybe 3mm runout about 150mm from the yoke and hell knows what the noise coming from inside it is.

Im a mechanic working for a place that builds high performance cars day in-day out and just hoped that a fresh set of eyes could give me some more educated ideas on what to target next. I was thinking about resetting the valve lash across the head as it does sound a bit rattly (head has also been replaced prior to me buying it) but as i am not thinking that its some kind of ignition system fault im not sure if this will actually help.

I was investigating the cam alignment this evening and with the crank at TDC, the cam pulley lines up with a notch to the cam cover notch, and after taking the oil cap off i could see a bit of a tab coming off the cam, which lined up with a marked arrow cast on a housing bolted to the cam cover. with these lined up, the rotor button was pointing at cylinder 4.


any help or ideas or suggestions are welcome! thanks.

[skyman]

Weak coil, or low fuel pressure? These two become apparent under load.

The fuel pressure regulators are known to be a pain on the american ones, and coils in these can go weak without dying.

[swifty_ano]

Replaced fuel filter?
Cleaned the throttle body and components?

[MacDaddy]

I had that misfire issue on my 89 Carby Vit, took me ages to work out, but it turned out to be the plastic cradle on the top of the engine, that all the spark plug leads sit in, it had broken off, and the leads were shorting out... at idle it was fine, but rev it, and it coughs and splutters... cable tied them back, and it worked fine !

[SuziBlu]

As I understand, it is fine under load, but on coast it misses, is that right ?

If so, thats got me beat. Normally its only under load that things go amiss.

[royce]

when you say misfire, can you sit in one rev and load point and it will carry on as long as you hold it there or is it a single glitch at one point and then is fine?

if you crawl it along like you are in traffic and lightly accelerate and decelerate does it do it each time you lightly push the throttle?

If so it sounds like what happens when the TPS is buggered or off adjustment, to fix mine I just moved it around till the idle started to rise from it then backed it off a bit and its been great since

[adsport]

suziblu : yep you got it.


skyman: Ive already had a fuel issue with the car, 3 days after buying it the fuel pump seized. I have a honda integra VTEC fuel pump in there now mostly because it was what was laying around and fit in without any real mods, so that should be good i think.


swifty: fuel filter might be one to look at but curiously it has no troubles starting or revving all the way to limiter when out of gear, and pulls clean all the way through the rev range when driving...

macbear : brand new leads all round!

royce : yeah if i sit in the range of 1200-1800 while loading it up and rolling it gives the impression of a misfire. I also thought of the TPS being out of adjustment because hell knows who has touched this motor before or what they have done to it. does anybody know the output voltage spec at 0% TPS ?

I'm used to dealing with Toyotas for which we have a of of detailed information on how to set up sensors so you can tell im not as converse with suzuki's yet. most toyotas have a TPS output of 0.5V at 0%.

thanks guys

[royce]

the tps has a switch for a seperate set of contacts at 0%, which mine measured all fine but twiddling it fixed it, 2 screws and a bit of a twist will tell you if you are at least on the right path

[adsport]

yep, these 4 wire TPS on the motor is the same as the 4AGE smallport motors that im used to which have the IDL (for idle fuel control map at 0% like you describe.

I found a manual which states that the 0% position should be "near to" 0V and a range of 3-5V which ties in to what i was thinking. im going to test the output voltage and give it a wiggle and see how that goes!

[adsport]

so to cut a long story short, i replaced the TPS with a toyota one, adjusted it to where it should be and it seems to be spot on .


thanks for the input from everybody, hopefully this issue doesn't come back.... hell knows how it got to be in a bad spot in the first place it doesn't seem like there would be any reason to remove or adjust the TPS in the first place but hey i've seen people do some weird stuff!

[nicktoozoff]

Noob question here, but what is "TPS"?

I also have a 1.6 EFI Vitara of about the same vintage. When it starts in the morning, it revs at around 1500-1800 RPM. After 10 minutes of running, the engine idle's at 500-800 RPM and seems to mis or cough. It occasionally does the same under loads of about 2000-2500 as well.

My symptoms seem similar to yours. Sorry to Hi-jack thread.

Cheers Nick.

[Damo]

nicktoozoff wrote:

Noob question here, but what is "TPS"?

I also have a 1.6 EFI Vitara of about the same vintage. When it starts in the morning, it revs at around 1500-1800 RPM. After 10 minutes of running, the engine idle's at 500-800 RPM and seems to mis or cough. It occasionally does the same under loads of about 2000-2500 as well.

My symptoms seem similar to yours. Sorry to Hi-jack thread.

Cheers Nick.

Throttle Position Sensor

[shandy92]

nicktoozoff wrote:

Noob question here, but what is "TPS"?

I also have a 1.6 EFI Vitara of about the same vintage. When it starts in the morning, it revs at around 1500-1800 RPM. After 10 minutes of running, the engine idle's at 500-800 RPM and seems to mis or cough. It occasionally does the same under loads of about 2000-2500 as well.

My symptoms seem similar to yours. Sorry to Hi-jack thread.

Cheers Nick.

Nick, that just sounds like the cold idle, but its a bit high tho. what have you replaced in trying to fix the issue? plugs, leads, cap, etc??

[adsport]

I would certainly start by giving your ignition system an overhaul if you haven't done so already. as shandy implies i think its always a good start to replace spark plugs and distributor cap and rotor, aswell as leads.

[nicktoozoff]

Have done nothing yet. Only owned the Vit for a month to date. Are those thing relatively easy to do? Not much good on the ol' spanners. But i have mates who can help out.

Cheers Nick

[MacDaddy]

nicktoozoff wrote:

Have done nothing yet. Only owned the Vit for a month to date. Are those thing relatively easy to do? Not much good on the ol' spanners. But i have mates who can help out.

Cheers Nick

Yep its all easy, just take off the old, put on the new... the hardest part is the plugs, you have to set the spark gap before you put the new ones in... and when you do the leads, do one at a time, so you know where they go, nothing worse than takin them all off and not know where the new ones go too...

[adsport]

the new leads i got were marked, aswell as the distributor cap! its hard to go wrong there hahah

the tip for young players with the spark plugs is to wind them in by hand until they start to get tight, as there should be very little resistance if you are doing it right.

also make sure that you get the correct cap and rotor combination for your car as there is a few different types. suzistore has a bit of a "how to identify" walk through on how to identify which distributor you have and thusly the correct bits to replace.

i owned my vit for less than a week before i got stuck in to replacing things hahah

[nicktoozoff]

Thanks guys.

[MacDaddy]

adsport wrote:

the new leads i got were marked, aswell as the distributor cap! its hard to go wrong there hahah

the tip for young players with the spark plugs is to wind them in by hand until they start to get tight, as there should be very little resistance if you are doing it right.

also make sure that you get the correct cap and rotor combination for your car as there is a few different types. suzistore has a bit of a "how to identify" walk through on how to identify which distributor you have and thusly the correct bits to replace.

i owned my vit for less than a week before i got stuck in to replacing things hahah

Thats the first i have heard of marked leads and dizzy cap... still a good idea to do them one by one...
Yep, agree with putting the plugs in by hand...
I owned my old Vit a month till i started replacing things, the new plugs, leads and dizzy cap rotor, made a big difference, plus a good oil change, with a bottle of Nulon engine oil cleaner, took 3 goes before it didnt go black within a week... do the air filter as well... oh and dont forget the fuel filter, mine had crumbled inside and was almost blocked...

[adsport]

diesel oil will do better than the nulon fix in a bottle, as it has active detergents .although i wouldnt say its a good idea to run diesel oil all the time it is good at flushing motors clean.

[MacDaddy]

adsport wrote:

diesel oil will do better than the nulon fix in a bottle, as it has active detergents .although i wouldnt say its a good idea to run diesel oil all the time it is good at flushing motors clean.

I will stick to the Nulon engine flush, at least i know it works, and works well, and is safe to use...

[shandy92]

MacBear wrote:

Yep its all easy, just take off the old, put on the new... the hardest part is the plugs, you have to set the spark gap before you put the new ones in... and when you do the leads, do one at a time, so you know where they go, nothing worse than takin them all off and not know where the new ones go too...

if ur buying the correct plug, this shouldnt need to be done. it should be at the right point from purchase. but just have a look and see if it need more or less. if so, just push it against something to close it, or use a screw driver or something flat to open it. just be careful, they are fragile and dont need to be moved much.

[MacDaddy]

shandy92 wrote:

MacBear wrote:

Yep its all easy, just take off the old, put on the new... the hardest part is the plugs, you have to set the spark gap before you put the new ones in... and when you do the leads, do one at a time, so you know where they go, nothing worse than takin them all off and not know where the new ones go too...

if ur buying the correct plug, this shouldnt need to be done. it should be at the right point from purchase. but just have a look and see if it need more or less. if so, just push it against something to close it, or use a screw driver or something flat to open it. just be careful, they are fragile and dont need to be moved much.

I have Never had a new plug, fresh out of the packet, set to the proper gap... screwdriver and pushing it, just isnt accurate enough for me, i use feeler gauges, and set them all to the proper gap, i want to extend the life of my engine components, not shorten their life with incorrect settings, so near enough aint good enough for me...

[SuziBlu]

MacBear wrote:

shandy92 wrote:

MacBear wrote:

Yep its all easy, just take off the old, put on the new... the hardest part is the plugs, you have to set the spark gap before you put the new ones in... and when you do the leads, do one at a time, so you know where they go, nothing worse than takin them all off and not know where the new ones go too...

if ur buying the correct plug, this shouldnt need to be done. it should be at the right point from purchase. but just have a look and see if it need more or less. if so, just push it against something to close it, or use a screw driver or something flat to open it. just be careful, they are fragile and dont need to be moved much.

I have Never had a new plug, fresh out of the packet, set to the proper gap... screwdriver and pushing it, just isnt accurate enough for me, i use feeler gauges, and set them all to the proper gap, i want to extend the life of my engine components, not shorten their life with incorrect settings, so near enough aint good enough for me...

X2, even the manufactures normally state, check to be sure.

Very easily bumped and closed.

[shandy92]

MacBear wrote:

shandy92 wrote:

MacBear wrote:

Yep its all easy, just take off the old, put on the new... the hardest part is the plugs, you have to set the spark gap before you put the new ones in... and when you do the leads, do one at a time, so you know where they go, nothing worse than takin them all off and not know where the new ones go too...

if ur buying the correct plug, this shouldnt need to be done. it should be at the right point from purchase. but just have a look and see if it need more or less. if so, just push it against something to close it, or use a screw driver or something flat to open it. just be careful, they are fragile and dont need to be moved much.

I have Never had a new plug, fresh out of the packet, set to the proper gap... screwdriver and pushing it, just isnt accurate enough for me, i use feeler gauges, and set them all to the proper gap, i want to extend the life of my engine components, not shorten their life with incorrect settings, so near enough aint good enough for me...

yeah i was just saying use this to get the two point within spec, but yeah use feeler gauges to check....how else would you??