Two issues

dnegative · 08-28-2009, 11:09 AM

First problem, once my car ('88 NA JDM) has warmed up when idling (at the lights, stopped etc) the idle will drop to ~500 rpm every now and then and surge back up to normal (1000 rpm give or take). I have a feeling its a coolant issue but before I go and drop money on new coolant is there anything else that could be causing it?

Second problem, at certain speeds (70km/h, 90km/h) there is sometimes a shuddering in the steering wheel. Lack of power steering combined with a 300mm wheel makes the issue more noticeable. Worth getting a wheel alignment done?

Cheers

muffinman · 08-28-2009, 11:16 AM

try bleeding the cooling system and see if it helps. jack the front end up and check that every ting is nice and tight.

dnegative · 08-28-2009, 11:25 AM

I was under the impression coolant had to be drained to remove any air bubbles? It needs a coolant change anyway

muffinman · 08-28-2009, 11:28 AM

if you haven't already done so , you should download the BGB it will be a life saver.

YellowJacket · 08-28-2009, 02:11 PM

check coolant first and bleed the air out is #1, but also the idle adjusting screw in throttle body is also something to play with...

dnegative · 08-29-2009, 02:08 AM

Went for a 40km spin and I couldn't get it to happen??? Bumped down the idle to 900rpm when hot. Odd....

Still leaking a bit of oil, not much I can do about that one though.

Dave In Indy · 08-30-2009, 04:33 PM

Have you checked your diagnostic codes?

YellowJacket · 09-02-2009, 02:06 PM

Sounds like your idle was just set too high. The ECU will cut off the fuel if there is no throttle and the RPM is above 1500 - once it drops it starts fuel again and the process repeats.

So if your cooling system is air-free you could have easily just had the idle set too high. But, you could also have air in your cooling system and you are compensating for that problem with the idle screw.... a bandaid.

Keep an eye on your coolant level in the FILLER NECK not the reservoir (although the reservoir needs to be properly full as well). If you are topping off due to mysterious missing coolant in the filler neck at regular intervals then you have a slow leak somewhere.

Shuddering could be bad tires, bad alignment, out of balance wheels, worn suspension parts, or bent rim... I had that problem and in my case, the old enkei rims that came on the car apparently were the cause. I got some Spyder rims and the shudder went away.

08-28-2009, 11:09 AM	#1 (permalink)
dnegative No Skills Join Date: Aug 2009 Posts: 4 Thanks: 1 Thanked 0 Times in 0 Posts iTrader Rating: (0/0% )	Two issues First problem, once my car ('88 NA JDM) has warmed up when idling (at the lights, stopped etc) the idle will drop to ~500 rpm every now and then and surge back up to normal (1000 rpm give or take). I have a feeling its a coolant issue but before I go and drop money on new coolant is there anything else that could be causing it? Second problem, at certain speeds (70km/h, 90km/h) there is sometimes a shuddering in the steering wheel. Lack of power steering combined with a 300mm wheel makes the issue more noticeable. Worth getting a wheel alignment done? Cheers

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08-28-2009, 11:16 AM	#2 (permalink)
muffinman U-P-G-R-A-Y-E-D-D Join Date: Jan 2008 Location: Sunny South Florida Posts: 5,880 Thanks: 53 Thanked 283 Times in 272 Posts Blog Entries: 1 My Google Map iTrader Rating: (2/100% )	try bleeding the cooling system and see if it helps. jack the front end up and check that every ting is nice and tight.

08-28-2009, 11:25 AM	#3 (permalink)
dnegative No Skills Join Date: Aug 2009 Posts: 4 Thanks: 1 Thanked 0 Times in 0 Posts iTrader Rating: (0/0% )	I was under the impression coolant had to be drained to remove any air bubbles? It needs a coolant change anyway

08-28-2009, 11:28 AM	#4 (permalink)
muffinman U-P-G-R-A-Y-E-D-D Join Date: Jan 2008 Location: Sunny South Florida Posts: 5,880 Thanks: 53 Thanked 283 Times in 272 Posts Blog Entries: 1 My Google Map iTrader Rating: (2/100% )	if you haven't already done so , you should download the BGB it will be a life saver.

08-28-2009, 02:11 PM	#5 (permalink)
YellowJacket 1985 16v NA 6-speed Join Date: Sep 2008 Location: Nashville, TN Posts: 415 Thanks: 8 Thanked 31 Times in 24 Posts iTrader Rating: (1/100% )	check coolant first and bleed the air out is #1, but also the idle adjusting screw in throttle body is also something to play with...

08-29-2009, 02:08 AM	#6 (permalink)
dnegative No Skills Join Date: Aug 2009 Posts: 4 Thanks: 1 Thanked 0 Times in 0 Posts iTrader Rating: (0/0% )	Went for a 40km spin and I couldn't get it to happen??? Bumped down the idle to 900rpm when hot. Odd.... Still leaking a bit of oil, not much I can do about that one though.

08-30-2009, 04:33 PM	#7 (permalink)
Dave In Indy Some Skills Join Date: Jun 2009 Posts: 61 Thanks: 1 Thanked 3 Times in 3 Posts iTrader Rating: (0/0% )	Have you checked your diagnostic codes?

09-02-2009, 02:06 PM	#8 (permalink)
YellowJacket 1985 16v NA 6-speed Join Date: Sep 2008 Location: Nashville, TN Posts: 415 Thanks: 8 Thanked 31 Times in 24 Posts iTrader Rating: (1/100% )	Sounds like your idle was just set too high. The ECU will cut off the fuel if there is no throttle and the RPM is above 1500 - once it drops it starts fuel again and the process repeats. So if your cooling system is air-free you could have easily just had the idle set too high. But, you could also have air in your cooling system and you are compensating for that problem with the idle screw.... a bandaid. Keep an eye on your coolant level in the FILLER NECK not the reservoir (although the reservoir needs to be properly full as well). If you are topping off due to mysterious missing coolant in the filler neck at regular intervals then you have a slow leak somewhere. Shuddering could be bad tires, bad alignment, out of balance wheels, worn suspension parts, or bent rim... I had that problem and in my case, the old enkei rims that came on the car apparently were the cause. I got some Spyder rims and the shudder went away.